The popular revolts shaking the Arab world have begun to shift the balance of power in the region, bolstering Iran’s position while weakening and unnerving its rival, Saudi Arabia, regional experts said.

While it is far too soon to write the final chapter on the uprisings’ impact, Iran has already benefited from the ouster or undermining of Arab leaders who were its strong adversaries and has begun to project its growing influence, the analysts said. This week Iran sent two warships through the Suez Canal for the first time since its revolution in 1979, and Egypt’s new military leaders allowed them to pass.

Saudi Arabia, an American ally and a Sunni nation that jousts with Shiite Iran for regional influence, has been shaken. King Abdullah on Wednesday signaled his concern by announcing a $10 billion increase in welfare spending to help young people marry, buy homes and open businesses, a gesture seen as trying to head off the kind of unrest that fueled protests around the region.

King Abdullah then met with the king of Bahrain, Hamad bin Isa al-Khalifa, to discuss ways to contain the political uprising by the Shiite majority there. The Sunni leaders in Saudi Arabia and Bahrain accuse their Shiite populations of loyalty to Iran, a charge rejected by Shiites who say it is intended to stoke sectarian tensions and justify opposition to democracy.

The uprisings are driven by domestic concerns. But they have already shredded a regional paradigm in which a trio of states aligned with the West supported engaging Israel and containing Israel’s enemies, including Hamas and Hezbollah, experts said. The pro-engagement camp of Egypt, Jordan and Saudi Arabia is now in tatters. Hosni Mubarak of Egypt has been forced to resign, King Abdullah of Jordan is struggling to control discontent in his kingdom and Saudi Arabia has been left alone to face a rising challenge to its regional role.

“I think the Saudis are worried that they’re encircled — Iraq, Syria, Lebanon; Yemen is unstable; Bahrain is very uncertain,” said Alireza Nader, an expert in international affairs with the RAND Corporation. “They worry that the region is ripe for Iranian exploitation. Iran has shown that it is very capable of taking advantage of regional instability.”

“Iran is the big winner here,” said a regional adviser to the United States government who spoke on the condition of anonymity because he was not authorized to speak to reporters.

Iran’s circumstances could change, experts cautioned, if it overplayed its hand or if popular Arab movements came to resent Iranian interference in the region. And it is by no means assured that pro-Iranian groups would dominate politics in Egypt, Tunisia or elsewhere.

For now, Iran and Syria are emboldened. Qatar and Oman are tilting toward Iran, and Egypt, Tunisia, Bahrain and Yemen are in play.

“If these ‘pro-American’ Arab political orders currently being challenged by significant protest movements become at all more representative of their populations, they will for sure become less enthusiastic about strategic cooperation with the United States,” Flynt Leverett and Hillary Mann Leverett, former National Security Council staff members, wrote in an e-mail.

They added that at the moment, Iran’s leaders saw that “the regional balance is shifting, in potentially decisive ways, against their American adversary and in favor of the Islamic Republic.” Iran’s standing is stronger in spite of its challenges at home, with a troubled economy, high unemployment and a determined political opposition.

The United States may also face challenges in pressing its case against Iran’s nuclear programs, some experts asserted.

“Recent events have also taken the focus away from Iran’s nuclear program and may make regional and international consensus on sanctions even harder to achieve,” Mr. Nader said. Iran’s growing confidence is based on a gradual realignment that began with the aftershocks of the Sept. 11 attacks. By ousting the Taliban in Afghanistan, and then Saddam Hussein in Iraq, the United States removed two of Iran’s regional enemies who worked to contain its ambitions. Today, Iran is a major player in both nations, an unintended consequence.

Iran demonstrated its emboldened attitude this year in Lebanon when its ally, Hezbollah, forced the collapse of the pro-Western government of Saad Hariri. Mr. Hariri was replaced with a prime minister backed by Hezbollah, a bold move that analysts say was undertaken with Iran’s support.

“Iraq and Lebanon are now in Iran’s sphere of influence with groups that have been supported by the hard-liners for decades,” said Muhammad Sahimi, an Iran expert in Los Angeles who frequently writes about Iranian politics. “Iran is a major player in Afghanistan. Any regime that eventually emerges in Egypt will not be as hostile to Hamas as Mubarak was, and Hamas has been supported by Iran. That may help Iran to increase its influence there even more.”

Iran could also benefit from the growing assertiveness of Shiites in general. Shiism is hardly monolithic, and Iran does not speak on behalf of all Shiites. But members of that sect are linked by faith and by their strong sense that they have been victims of discrimination by the Sunni majority. Events in Bahrain illustrate that connection well.

Bahrain has about 500,000 citizens, 70 percent of them Shiite. The nation has been ruled by a Sunni family since it was captured from the Persians in the 18th century. The Shiites have long argued that they are discriminated against in work, education and politics. Last week, they began a public uprising calling for democracy, which would bring them power. The government at first used lethal force to try to stop the opposition, killing seven. It is now calling for a dialogue while the protesters, turning out in huge numbers, are demanding the government’s resignation.

But demonstrators have maintained their loyalty to Bahrain. The head of the largest Shiite party, Al Wefaq, said that the party rejected Iran’s type of Islamic government. On Tuesday, a leading member of the party, Khalil Ebrahim al-Marzooq, said he was afraid that the king was trying to transform the political dispute into a sectarian one. He said there were rumors the king would open the border with Saudi Arabia and let Sunni extremists into the country to attack the demonstrators.

“The moment that any border opens by the government, means the other borders will open,” he said. “You don’t expect people will see their similar sect being killed and not interfere. We will not call them.”

But, he said, they will come.