Two months after the eruption of mass protests in Bahrain, the kingdom has largely silenced the opposition, jailing hundreds of activists in a crackdown that has left the Obama administration vulnerable to charges that it is upholding democratic values in the Middle East selectively.

Bahrain's monarchy, since calling in Saudi troops last month to help crush the protest movement, has been quietly dismantling the country's Shiite-led opposition. On Friday, the Sunni government announced an investigation into the activities of Bahrain's largest political party, the Shiite-dominated al-Wefaq, which could lead to its ban.

The Obama administration has repeatedly appealed to the Bahraini government for restraint, and Secretary of State Hillary Rodham Clinton this week called for a political process that "advances the rights and aspirations of all the citizens of Bahrain." But the administration has neither recalled its ambassador to Manama nor threatened the kinds of sanctions it imposed on Libya - a striking disparity that is fueling ­anti-U.S. sentiment among Bahraini opposition groups.

"Even though the American administration's words are all about freedom and democracy and change, in Bahrain, the reality is that they're basically a protection for the dictatorship," said Zainab al-Khawaja, a prominent human-rights activist who began a hunger strike after her father, husband and brother-in-law were arrested at her apartment over the weekend.

U.S. officials privately acknowledge that the administration has been understated in its criticism of Bahrain, in part to avoid further strain in relations with Saudi Arabia, a vital U.S. ally and neighbor to the tiny island kingdom. The Saudis, fearing the rise of a pro-Iranian Shiite state on its eastern frontier, urged Bahrain to deal firmly with the throng of protesters that occupied a central square and blocked access to Manama's main business district.

A month later, however, with Bahrain's iron first tightening further, the White House is facing awkward questions from political allies as well as foes. A perceived U.S. double standard on Middle East democracy - a problem since the Arab spring movement began three months ago - could become more acute if Washington is seen to ignore widespread abuses, according to current and former diplomats and regional experts.

"We need to worry about the human-rights situation deteriorating there," said Joel Rubin, a former Middle East specialist for the State Department and deputy director of the National Security Network, a Democratic-leaning foreign policy think tank. "It has a real impact on perceptions of American policy in the region."

U.S. officials defend the administration's ad hoc approach to Middle East democracy movements as prudent, saying each country requires a unique balancing of democratic ideals and compelling security interests.

"We don't make decisions about questions like intervention based on consistency or precedent," Denis R. McDonough, Obama's deputy national security adviser, said recently in explaining why U.S. policy on Libya differs from that on Bahrain. "We make them based on how we can best advance our interests in the region."

In the case of Bahrain, the United States has key military interests. The kingdom is home to the U.S. Navy's 5th Fleet; it is also seen as a strategically important bulwark against Iranian power in the region. But even more vital is the U.S. relationship with Saudi Arabia, a critical ally in the Middle East for half a century.

Saudi Arabia and the United States have fundamentally different views of what is happening in Bahrain, why it is happening and who is responsible for it. Saudi officials deny that Bahrain has cracked down on legitimate demonstrators, insisting that action has been taken only against radicals seeking to provoke the government. A senior U.S. official held the opposite view, saying: "The crackdown is a fact."

Administration officials accept that Bahrain is the Saudi "back yard," a point emphasized by a member of the Saudi legislative council, Majlis al-Shura, during a visit to Washington last week. "Bahrain is our Cuba," said the official, who spoke at a forum organized by the New America Foundation.

"We don't believe the uprising is real," said another shura member. Most of Bahrain's Shiites "are happy; a small minority is causing the problem," he said. "Maybe some are oppressed, but 1 percent is causing the trouble."

Whatever the makeup of the protest movement, the intensity of the crackdown stunned Bahraini opposition leaders as well as many Middle East experts, who are dismayed by the dismantling of reforms that had cemented the island's reputation as progressive and Western-friendly. Until the crackdown on March 14, many of the thousands of protesters who jammed the capital's Pearl Square were confident that the movement sweeping the region would bring new political freedoms and economic equality for the country's majority Shiite population.

"Only a month ago, we had a feeling of change and respect for democracy and human rights. Now we feel as though we are all in a big prison," said Mohammed al-Maskati, president of the Bahrain Youth Society for Human Rights. "They want to attack everyone who was involved in the protests."

In addition to jailing activists and banning Shiite-led opposition parties, Bahraini authorities fired civil servants and even professional athletes who participated in demonstrations.

The country's only independent newspaper was taken over last week and its editor forced to resign. And on Monday, the New York-based Human Rights Watch alleged that at least three opposition figures had died in Bahraini prisons under suspicious circumstances. While Bahraini authorities attributed the deaths to natural causes, Human Rights Watch said in a report that one of the victims' bodies bore "signs of horrific abuse."

Some government opponents accuse the United States of failing to put enough pressure on Bahrain and the neighboring Persian Gulf kingdoms that supported the crackdown. One prominent human rights activist described Bahraini protesters as "very, very disappointed" by the mild American response.

Clinton defended the U.S. role in a speech this week at a meeting of the U.S.-Islamic World Forum, insisting that the United States' "core interests and values have not changed, including our commitment to promote human rights." But Clinton cited other goals, including the defeat of terrorism and the containment of Iran, as "mutual interests."

"We know that a one-size-fits-all approach doesn't make sense in such a diverse region at such a fluid time," she said.

Clinton mentioned Bahrain only briefly, hailing what she called a "decades-long friendship with Bahrain that we expect to continue long into the future." But, referring to the recent crackdown, she added that "violence is not and cannot be the answer."

"We have raised our concerns about the current measures directly with Bahraini officials and will continue to do so," Clinton said.

Birnbaum reported from Berlin. Staff writer Karen DeYoung in Washington contributed to this report.