"The danger is privacy is being invaded. It's a program of big, big brother," Specter told CBS television.

Coming on the heels of recent revelations that Bush had allowed eavesdropping on telephone calls to foreign destinations without court warrants, Bush sought to head off possible political damage with a hastily arranged appearance before reporters.

Bush did not deny or confirm the existence of the world's largest database, which USA Today said was set up after the September 11, 2001 attacks.

But he asserted that the US intelligence community is not "mining or trolling" through the private lives of Americans, simply attempting "to intercept the communications of people with known links to Al-Qaeda and related terrorist organizations."

"After September 11, I vowed to the American people that our government would do everything within the law to protect them against another terrorist attack," Bush said at the White House.

"If Al-Qaeda or their associates are making calls into the United States or out of the United States, we want to know what they're saying," he said.

Bush sought to reassure the public that "the privacy of ordinary Americans is fiercely protected," under the anti-terrorism programs.

Opposition Democrats seized on the report as further proof that the Bush administration was flouting civil liberties under a veil of secrecy.

"We are on our way to a major constitutional confrontation on Fourth Amendment guarantees on unreasonable search and seizure," Senator Dianne Feinstein said.

The California lawmaker also said the disclosure of the program could derail confirmation of Bush's nominee to take over as director of the CIA, General Michael Hayden.

As the current head of the National Security Agency, Hayden has overseen the eavesdropping and database monitoring efforts that have raised concerns among both Republicans and Democrats in Congress.

Hayden avoided commenting on the newspaper report but told reporters that "everything the NSA does is lawful and very carefully done."

Top Democrats questioned the rationale and the legality of the operation and demanded the Republican leadership hold the Bush administration accountable.

"Unfortunately, the Congress has acted like a wholly-owned subsidiary of the White House and has rubber-stamped everything that's gone on. And then we find out everything through the press, whoops, they weren't following the law," said Democratic Senator Patrick Leahy told PBS's "The Newshour with Jim Lehrer."

Bush, whose poll ratings have steadily plunged in the past year, was thrown on the defensive in December by reports on the eavesdropping on foreign telephones calls without warrants from a special court.

But as with the previous case, the White House and its allies insisted the effort was entirely legal and condemned those who had leaked the operation's details as jeopardizing national security.

White House spokeswoman Dana Perino said leaking sensitive information to the media "hurts our ability to defeat this enemy."

While the eavesdropping program revealed by The New York Times last year affected thousands of US citizens, the program outlined by USA Today detailed an NSA database of tens of millions of US phone customers.

The newspaper quoted sources as saying the NSA analyzed the calling patterns of records provided by the AT and T, Verizon and BellSouth companies. One telephone company, Qwest, turned down a request to hand over phone records, the paper wrote.

Names, addresses and other forms of personal identification are not part of the information, the report said, but it noted that those details can be easily obtained by cross-checking the records against other databases.

A civil liberty group filed a class-action lawsuit against AT and T in January accusing the telecom giant of violating the law and its customers' privacy by "collaborating with the NSA."

Ever since news of the surveillance program became public in December, the president and members of his administration have stressed that it was limited to intercepting phone conversations and e-mail messages where one party to the conversation was outside the United States. In January, Bush assured Americans that "one end of the communication must be outside the United States."

Bush did not dispute the latest allegations and said that "the intelligence activities I authorized are lawful and have been briefed to appropriate members of Congress, both Republican and Democrat." He did warn that when information such as this is leaked, the government's ability to defeat terrorists is threatened.

Thursday's report could complicate the Bush administration's defense of the program and the Senate confirmation of Michael Hayden, who was at the helm of the NSA during the creation of the program and was nominated by Bush to be CIA chief last week. Senate confirmation hearings for Hayden will be overseen by Arlen Specter, the Republican head of the Senate Judiciary Committee, who recently threatened to eliminate funding for the spy program, unless congressional questions about it were answered.

Citing unnamed sources with knowledge of the program, USA Today said the telephone companies had divulged "call detail records," which are database entries that record the parties to the conversation, the length of the call, and so on. That would mean that the NSA and other government agencies would have records of the calling histories of hundreds of millions of Americans--though without access to the actual content of the conversations.

A CNET News.com survey published in February asked telecommunications carriers whether they had "turned over information or opened up their networks to the NSA without being compelled by law?" Neither Verizon nor AT&T would give a "yes" or a "no" answer to that question.

But BellSouth did answer in the negative at the time. A BellSouth representative did not immediately respond to follow-up questions on Thursday.

USA Today reported that Qwest Communications International was approached but that Qwest's CEO at the time, Joe Nacchio, was deeply troubled by the NSA's assertion that no court authorization was necessary. In News.com's survey, Qwest also responded with a "no" answer.

Section 222 of the Communications Act (click here for PDF) generally prohibits phone companies from divulging customer information "except as required by law." It's unclear whether an executive order qualifies as a legal requirement, and fines could in theory be substantial.

The Electronic Frontier Foundation, a civil liberties group in San Francisco, filed a class action lawsuit against AT&T in January, saying the company violated federal privacy laws. But the Bush administration said on April 28 that it will attempt to have the suit tossed out of court because it could reveal "state secrets."

Officials at the Foreign and Commonwealth Office said yesterday that Señor Chávez was on a private visit, similar to other world leaders who come to London for shopping trips or medical treatment.

The difference this time, however, is that the Venezuelan head of state will hardly be keeping a low profile as he attends an exhausting round of public engagements, many of them only a short distance from Downing Street.

On Sunday Señor Chávez is due to address supporters in Westminster. On Monday he meets the TUC, gives a press conference at City Hall with the Mayor and visits MPs at the House of Commons. On Tuesday he opens a museum and makes a speech in Whitehall.

Venezuelan officials said that the trip had been made at the request of Señor Chávez to thank his supporters in Britain, many of them on the Left of the Labour Party. This visit is certainly in contrast to his first, in 2001, when he was welcomed by Mr Blair, dined with John Prescott, the Deputy Prime Minister, and had an audience with the Queen.

Relations soured over Britain's involvement in Iraq and London's growing criticism of Señor Chávez, who has used Venezuela's oil wealth to push a left-wing movement across Latin America that he has nicknamed the "axis of good".

In 2002 Denis MacShane, then a junior Foreign Office minister, compared Señor Chávez to Mussolini, and described him as a "ranting, populist demagogue".

In February this year Mr Blair advised the President to "abide by the rules of the international community". The next day Señor Chávez demanded that Britain return the Falkland Islands to Argentina and stop behaving as an imperialist power. "Tony Blair, you have no moral right to tell anyone to respect international laws, as you have shown no respect for them, aligning yourself with 'Mr Danger' [President Bush] and trampling on the people of Iraq," he said. "Do you think we still live in the times of the British Empire or colonialism?" Any repeat of his claims in London may embarrass the Prime Minister but will be cheered by the President's supporters, who regard his global movement as a challenge to the policies of the Bush Administration.

"There are many areas where we can benefit from the Venezuelan experience - including energy and environmental policies, democratic participation and, of course, his Government's remarkable achievements in eliminating illiteracy, widening access to education and extending free healthcare to the majority of the population for the first time," Mr Livingstone said.

Colin Burgon, MP for Elmet and chairman of Labour Friends of Venezuela, said that Señor Chávez had an important message to deliver in Britain and that the Prime Minister was wrong to criticise him.

"When one considers that Hugo Chávez won an electoral majority in 2002, survived an attempted coup thanks to massive public protests and was the resounding winner of a referendum on his administration in 2004, the implied accusation seems inaccurate," he said.

"Our party should support the mobilisation of wide-reaching free healthcare and education schemes aimed at the reversal of decades of social inequality in South and Central America. It is time that the UK re-engaged with Latin America and offered moral support to regimes intent on social justice and redistribution of wealth."

Since March, the Maricopa County Sheriff's Office has arrested 147 illegal immigrants and smugglers under the law as contentiously interpreted by Maricopa County Attorney Andrew Thomas.

Thomas argues that the smuggling law can be applied to the smuggled immigrants themselves. By paying a smuggler to enter the country, Thomas says an illegal immigrant is committing conspiracy to smuggle, punishable by up to 2 years in jail.

The sheriff's office announced last week that it would dedicate an entire posse to arresting illegal immigrants under the law.

"We're going to arrest any illegal who violates this new law," Arpaio said. "I'm not going to turn these people over to federal authorities so they can have a free ride back to Mexico. I'll give them a free ride into the county jail."

At the launch Wednesday night, Arpaio told the sheriff's posse to not worry about costs or jail space, but to arrest as many illegal immigrants as they found.

But only one man would be arrested.

Deputies attempted to pull over a pickup truck around 12:45 a.m. Thursday, but the truck took off in the desert and its 15 to 20 occupants scattered.

Only one of them was tracked down despite night vision equipment, spotlights and a helicopter.

To say the least, it was a disappointment.

"It just makes me angry," Arpaio said Thursday. "People say these are helpless people coming into the United States just to work, and yet when they see law enforcement, they run. If they were trying to obey the law, why are they running?

"That doesn't make me happy," he continued. "We didn't catch anybody else, and I don't know why."

Arpaio speculated that the night was slow because potential border crossers have heard that if they're caught his county, they won't get very far.

Then again, maybe it was just a slow night, he said. Either way, the posse will continue its patrols for illegal immigrants.

"This isn't a one-night operation," Arpaio said. "We're going to keep going and keep booking them into the county jail. We're up to 147. I don't care if we go to 1,000 or 2,000 illegals. We'll make room for them. I've got a lot of tents out there."

The Center for Human Rights and Constitutional Law in Los Angeles is challenging the application of the smuggling law to illegal immigrants.

"You cannot charge someone with conspiracy to violate a law that inherently involves two people, because then you could just charge every single person involved with conspiracy," said Peter Schey, president of the human rights group. "Say you have an adult participating in consensual sex with a 16-year-old. You can't charge the 16-year-old with conspiracy to commit statutory rape."