The war in Iraq is a major political issue for the November 7 legislative and gubernatorial elections, with opposition Democrats calling for the start of a US withdrawal and opinion polls showing public disquiet over the US presence in Iraq.

Bush's Republican party, anxious to retain its majority in Congress, and his administration have set out to persuade American voters that Iraq is part of the "war on terror." They hope to repeat previous successes in elections in 2002 and 2004 when voters expressed more confidence in Bush and the Republicans to safeguard the country against possible terrorist attack.

"The central front on the war on terror, now, is Iraq," Bush told the partisan audience.

"If we were to leave before the mission is complete, it would hurt US credibility," he added. "Who would want to stand with the United States of America if we didn't complete the mission, and a mission that can be completed and will be completed?"

Earlier on Wednesday, the White House flatly denied reports that Bush was frustrated with Iraqis and their prime minister, and rejected the notion that Iraq has plunged into civil war.

The New York Times, citing anonymous participants in Bush's closed-door meeting with Iraq experts this week, reported earlier that the US president had expressed frustration with the pace of progress in Iraq and with Maliki.

"We don't expect him to be an overnight success in dealing with all these problems -- nobody can be. But the president certainly supports Prime Minister Maliki," countered White House spokesman Tony Snow.

"You've got a government that is brand new," Snow told reporters. "This is a guy who has a series of challenges before him with his government, and the president is impressed not only by his determination to get the job done, but the fact is that he is working aggressively to do these things."

Bush believes that "when you're facing a situation, you don't sit around and get frustrated. You figure out how to get the job done," said Snow. "The president is somebody who's intensely practical about these things."

Opposition Democratic lawmakers have accused Bush's government of diverting resources from the hunt for
Osama bin Laden and his Al-Qaeda network, which carried out the September 11, 2001 attacks, to the 2003 invasion to topple Iraqi dictator Saddam Hussein.

But Bush insisted that the war in Iraq was part of the broader battle against terrorist threats.

"It's important to understand this is a global war on terror, not an isolated moment of law enforcement. This is the first war of the 21st century and the United States of America must lead that war, and we must be firm, and we must be resolved."

Washington says Baghdad is key to stability in the entire country and stressed it was keeping faith with Maliki.

"(President George W Bush) is impressed not only by his determination to get the job done, but the fact is that he is working aggressively to do these things," said White House spokesman Tony Snow in Washington.

The new Shi'ite-led government has promised to reconcile Iraq's rival sects but almost three months after Maliki took power, the bloodshed continues.

Simultaneous car bombs killed 13 and injured 43 in a busy commercial area of central Baghdad, police said.

Earlier on Wednesday, a roadside bomb in a small flea market in east Baghdad killed eight and wounded up to 28.

"The bomb exploded beside those people who were just here to earn their living. They were just selling junk," said Mohamed Karin, standing amid the scattered debris of old televisions and household utensils.

"An old man with his two kids were killed. What did they do? They were innocent," he said.

STREET FIGHTING

Fighting in Basra began with an attack on the office of the governor and governing council. Basra Governor Mohamed Alwaili said they were mainly from the powerful Bani-Asad tribe and police sources said they were avenging the killing of a leader.

"There were men from this tribe and others from Basra. They started shooting at the governor's building. We will stand firm against those who carry weapons," he said.

Aqil al-Furaiji, a member of the Shi'ite-led governing council, said one policeman was killed and five wounded. Television pictures showed Iraqi forces exchanging heavy fire while two British armored personnel carriers passed.

The British military said up to 180 British soldiers and 16 Warrior armored personnel carriers had been dispatched to back up Iraqi troops and police on the ground.

Major Charlie Burbridge said that British forces exchanged several minutes of fire with some of the armed fighters as they departed Basra, but no soldiers were wounded.

Wednesday's fighting followed violence in the normally quiet southern shrine town of Kerbala on Tuesday between the Iraqi Army and followers of a radical Shi'ite cleric.

The Iraqi Defense Ministry said on Wednesday 12 people were killed in the incident, including two policemen.

Kerbala police deployed more than 10,000 troops and officers in a security cordon around the city to stop several thousand followers of the cleric, Mahmoud al-Hasani, from returning after a march in the nearby town of Hilla.

The bomb statistics - compiled by American military authorities in Baghdad and made available at the request of The New York Times - are part of a growing body of data and intelligence analysis about the violence in Iraq that has produced somber public assessments from military commanders, administration officials and lawmakers on Capitol Hill.

"The insurgency has gotten worse by almost all measures, with insurgent attacks at historically high levels," said a senior Defense Department official who agreed to discuss the issue only on condition of anonymity because he was not authorized to speak for attribution. "The insurgency has more public support and is demonstrably more capable in numbers of people active and in its ability to direct violence than at any point in time."

A separate, classified report by the Defense Intelligence Agency, dated Aug. 3, details worsening security conditions inside the country and describes how Iraq risks sliding toward civil war, according to several officials who have read the document or who have received a briefing on its contents.

The nine-page D.I.A. study, titled "Iraq Update," compiles the most recent empirical data on the number of attacks, bombings, murders and other violent acts, as well as diagrams of the groups carrying out insurgent and sectarian attacks, the officials said.

The report's contents are being widely discussed among Pentagon officials, military commanders and, in particular, on Capitol Hill, where concern among senior lawmakers of both parties is growing over a troubling dichotomy: even as Iraq takes important steps toward democracy - including the election of a permanent government this spring - the violence has gotten worse.

Senior Bush administration officials reject the idea that Iraq is on the verge of civil war, and state with unwavering confidence that the broad American strategy in Iraq remains on course. But American commanders in Iraq have shifted thousands of soldiers from outlying provinces to Baghdad to combat increased violence in the Iraqi capital.

The increased attacks have taken their toll. While the number of Americans killed in action per month has declined slightly - to 38 killed in action in July, from 42 in January, in part reflecting improvements in armor and other defenses - the number of Americans wounded has soared, to 518 in July from 287 in January. Explosive devices accounted for slightly more than half the deaths.

An analysis of the 1,666 bombs that exploded in July shows that 70 percent were directed against the American-led military force, according to a spokesman for the military command in Baghdad. Twenty percent struck Iraqi security forces, up from 9 percent in 2005. And 10 percent of the blasts struck civilians, twice the rate from last year.

Taken together, the new assessments by the military and the intelligence community provide evidence that violence in Iraq is at its highest level yet. And they describe twin dangers facing the country: insurgent violence against Americans and Iraqi security forces, which has continued to increase since the killing on June 7 of Mr. Zarqawi, the leader of the insurgent group Al Qaeda in Mesopotamia, and the primarily sectarian violence seen in Iraqi-on-Iraqi attacks being aimed at civilians.

Iraq is now locked in a cycle in which strikes by Sunni Arab militants have prompted the rise of Shiite militias, which have in turn aggravated Sunni fears. Beyond that, many Sunnis say they believe that the new Shiite-dominated government has not made sufficient efforts to create a genuine unity government. As a result, Sunni attitudes appear to have hardened.

As the politics in Iraq have grown more polarized since the elections in December, in which many Sunni Arabs voted, attacks have soared, including sectarian clashes that have killed an average of more than 100 Iraqi civilians per day over the past two months.

In addition to bombs, attacks with mortars, rocket-propelled grenades and small-caliber weapons against American and Iraqi military forces have also increased, according to American military officials. But the number of roadside bombs - or improvised explosive devices as they are known by the military - is an especially important indicator of enemy activity. Bomb attacks are the largest killer of American troops. They also require a network: a bomb maker; financiers to pay for the effort; and operatives to dig holes in the road, plant the explosives, watch for approaching American and Iraqi forces and set off the blast when troops approach.

With the violence growing in Iraq, American intelligence agencies are working to produce a National Intelligence Estimate about the security conditions there - the first such formal governmentwide assessment about the situation in Iraq since the summer of 2004.

In late July, D.I.A. officials briefed several Senate committees about the insurgent and sectarian violence. The presentation was based on a draft version of what became the Aug. 3 study, and one recipient described it as "extremely negative." That presentation was followed by public testimony on Aug. 3 by Gen. John P. Abizaid, the top American military commander in the Middle East, who told the Senate Armed Services Committee that the sectarian violence was "probably as bad as I've seen it, in Baghdad in particular" and said if it was not stopped, "it is possible that Iraq could move towards civil war." General Abizaid later emphasized that he was "optimistic" that the slide toward civil war could be prevented.

Officials who have read or been briefed on the new D.I.A. analysis said its assessments paralleled both aspects of General Abizaid's testimony.

The newest accounts of the risks of civil war may already be altering the political dynamic in Washington. After General Abizaid's testimony, the chairman of the Armed Services Committee, Senator John W. Warner of Virginia, said that if Iraq fell into civil war, the committee might need to examine whether the authorization provided by Congress for the use of American force in Iraq would still be valid. The comments by Senator Warner, a senior Republican who is a staunch supporter of the president, have reverberated loudly across Congress.

Bush administration officials now admit that Iraqi government's original plan to rein in the violence in Baghdad, announced in June, has failed. The Pentagon has decided to rush more American troops into the capital, and the new military operation to restore security there is expected to begin in earnest next month.

Yet some outside experts who have recently visited the White House said Bush administration officials were beginning to plan for the possibility that Iraq's democratically elected government might not survive.

"Senior administration officials have acknowledged to me that they are considering alternatives other than democracy," said one military affairs expert who received an Iraq briefing at the White House last month and agreed to speak only on condition of anonymity.

"Everybody in the administration is being quite circumspect," the expert said, "but you can sense their own concern that this is drifting away from democracy."