A month after a brutal crackdown on Shiite protesters there, Bahrain is exacerbating tensions between Saudi Arabia and Iran, dragging relations between the Persian Gulf rivals to their lowest level in at least a decade and setting the stage for confrontations elsewhere in the region.

On Friday, a large crowd of students rallied outside the Saudi Embassy in Tehran, chanting “Death to al-Saud” in what official news accounts described as a three-day sit-in protesting the suppression of anti-government demonstrations in Bahrain. The latest protests capped a week of rising tensions in which Iranian youths hurled stones and firebombs at the Saudi Embassy while Riyadh threatened to withdraw its diplomats.

Although few think that an armed clash between the two countries is likely, U.S. officials and Middle East experts see the beginnings of a prolonged freeze in diplomatic relations along with growing risks of conflict between proxy groups in a region where Iranian-backed Shiites and Saudi-funded Sunnis have long competed for dominance.

“The real battlefields are in Lebanon, Iraq and Bahrain,” said Karim Sadjadpour, an Iran expert at the Washington-based Carnegie Endowment for International Peace. Each country is seeking to blame the other for stirring up trouble in the region, with Iran portraying the Bahraini uprising as a “war against corruption and imperialism” while the Saudis see a broad conspiracy by Iranian Shiites to expand their influence, he said.

Iran and Saudi Arabia have been in regional competition for decades. Both nations depend heavily on oil revenue, which Iran has employed for keeping its 1979 Islamic revolution afloat, while Saudi Arabia has used its oil and financial leverage to position itself as a main ally of the United States in the Persian Gulf region.

With the fall of other Sunni bulwarks, including Saddam Hussein in Iraq and Hosni Mubarak in Egypt, Saudi Arabia increasingly regards itself as the last defense against Iranian dominance in the region.

For now, the focal point of the conflict between Iran and Saudi Arabia is Bahrain, the tiny island kingdom that is tethered to Saudi Arabia by a 16-mile causeway and is home to the U.S. Navy’s 5th Fleet. Responding to an appeal from Bahrain’s Sunni monarchy, at least 1,000 Saudi troops entered Bahrain on March 14 to help drive out protesters who had paralyzed the capital’s central business district for nearly a month.

After crushing the uprising, Bahraini security forces began systematically dismantling its support network, closing independent news outlets, arresting activists and moving to outlaw opposition political parties.

The moves drew condemnation from Iran, while Bahrain and other gulf states in turn accused Tehran’s ruling Shiite clerics of secretly backing the uprising. Since the crackdown, Bahrain has remained relatively calm, at least on the surface, while the war of words between Iran and Saudi Arabia has continued to escalate.

After rock-throwing clashes last week in front of the Saudi Embassy in Tehran, Saudi Arabia’s deputy foreign minister, Prince Turki bin Mohammed, warned that Riyadh would be “obliged to withdraw our diplomatic mission from Tehran” if the embassy continues to be attacked.

Top Iranian lawmakers and military officials fired back with a volley of criticism against Saudi rulers that included a veiled warning about a possible Bahrain-style uprising in the Saudi kingdom.

“Saudi Arabia may come under invasion for the very same excuse,” Maj. Gen. Yahya Rahim Safavi, a senior military adviser to Iran’s supreme leader, Ayatollah Ali Khamenei, said Monday.

Iranian President Mahmoud Ahmadinejad, who rarely misses an opportunity for heated rhetoric, has remained relatively restrained. Two weeks after Saudi armored personnel carriers rolled in to the Bahraini capital, Manama, he denounced the crackdown as “an ugly thing.” Ahmadinejad has also cautioned against what he calls a U.S. conspiracy to create divisions among Muslims along sectarian lines. “Don’t be fooled by them,” he said recently, referring to the West. “Iran is a friend of all nations.”

In the past two weeks, a variety of lower-ranking Iranian officials have lashed out repeatedly against Bahrain and the Gulf Cooperation Council. The six GCC countries — Saudi Arabia, Kuwait, Bahrain, the United Arab Emirates, Qatar and Oman — earlier issued a joint statement accusing Iran of fomenting plots, hatching conspiracies and running spy rings. The statement demanded that Iran “stop interfering” in the affairs of its gulf neighbors.

U.S. officials have been generally skeptical about claims that Iran was behind the Bahrain uprising, although Defense Secretary Robert M. Gates, during a visit to the gulf this month, said he had seen “evidence that the Iranians are trying to exploit the situation in Bahrain.” He did not elaborate.

Defending his country’s crackdown on protesters, Bahraini Foreign Minister Khalid bin Ahmad al-Khalifa said Monday that the troops would remain on the island until Iranian “threats” have been eased. Bahrain and Iran have a long history, with Iran at several times laying claim on the island. Relations have been cold in the past decade, with very few Iranians being able to obtain visas for the country.

Within hours of Khalid’s remarks, an Iranian Foreign Ministry spokesman fired back with a statement dismissing the GCC complaints, saying it was the Arabs who were doing all the interfering in the region.

“The military forces of some members of the council have disregarded international law and conventions, interfered in the internal affairs of their neighboring country and cracked down on defenseless men and women,” the spokesman, Ramin Mehmanparast, told reporters.

Some factions with the Iranian government — including prominent allies of Ahmadinejad — are demanding a harder line against Saudi Arabia, tacitly backing the actions of students who attacked the Saudi Embassy compound with rocks and Molotov cocktails before being driven back by riot police.

Rouhollah Hosseinian, an Ahmadinejad supporter in parliament, has called for Iran’s forces to be prepared for war. “We should not allow Saudi Arabia’s borders to get closer to us,” Hosseinian told the Khabar Online Web site.

An influential Shiite activist, Hossein Allahkaram, said Sunday that Iran has a range of methods to drive the Saudis out of Bahrain, with the ultimate option being suicide bombings.

Other factions have sought to tone down the rhetoric, noting that the wave of unrest spilling through the Middle East has already strengthened Iran’s hand at the expense of longtime rivals Egypt and Iraq.

“Let’s face it: Saudi Arabia is hugely unstable and now tries to create a mythological enemy to cover up its increasing weaknesses,” said Mohammad Marandi, a professor of North American studies at Tehran University. He said domestic unrest combined with the regional uprisings are increasingly making Saudi Arabia’s rulers nervous.

“Iran does not need to react or give any excuses or pretexts for the Saudis,” Marandi said. “In the end, it is them who are really in trouble.”

Despite past antagonism toward Iran — the Saudis briefly banned Iranians from making religious pilgrimages to Mecca after Iranian groups staged protests against the Saudi royal family in the late 1970s — Saudi Arabia has in recent years refrained from openly criticizing its Shiite neighbor, said David B. Ottaway, a Middle East expert at the Woodrow Wilson International Center for Scholars and author of “The King’s Messenger,” a book on U.S.-Saudi relations.

Ottaway characterized the deepening conflict over Bahrain as the start of a “political and religious cold war.”

“They have always wanted to keep things friendly, saying that today’s enemy may be tomorrow’s friend,” Ottaway said. “Now for the first time, you hear Saudi diplomats talking about ‘red lines.’ And for them, Bahrain is a red line.”

Warrick reported from Washington.