With Iran Ascendant, U.S. Is Seen at Fault

The result? "A disaster," he said. "Disaster."

'Defensive' Alliance

Mirzai, the former Iranian diplomat, offered a similar scenario in more threatening terms. Wearing a white turban and the robes of a cleric, he sketched out potential Iranian responses: cutting the Strait of Hormuz in the Persian Gulf, through which 20 percent of the world's oil passes; retaliation in Iraq, Afghanistan or Lebanon; attacks on U.S. targets in the Gulf.

"There is a policy the Iranians have and they've repeated it often -- the Gulf is either safe for everyone or no one," he said.

In an attempt to contest Iran's influence, the United States has sought to form an axis among Sunni Arab states it considers moderate: Egypt, Jordan, Saudi Arabia and smaller countries in the Gulf. Israeli officials have spoken about a possible alignment of their country's interests with those states to arrest both Iran's influence and its nuclear program.

In November, Israeli Prime Minister Ehud Olmert said he would try to deepen ties with those states, some of which have yet to recognize Israel, in what Israeli analysts saw as an opening bid to create an anti-Iranian bloc.

But Zisser, of Tel Aviv University, cautioned that "all of these countries are not very strong, and they have their own problems."

"Iran's threat could do something to bring them together, but I would say that any alliance that comes out of it would be defensive in nature," he said. "These countries are not going to be able to unite in any way that would meaningfully change the face of the Middle East."

Potentially more far-reaching is the sectarian tension that the struggle has ignited. In the Palestinian territories, Israeli officials say, Iran has been increasingly successful in influencing the chaotic political situation, particularly by funding the Hamas-led government.

The connection has not gone unnoticed in the Palestinian street. At two rallies this month for Fatah, the movement led by Palestinian Authority President Mahmoud Abbas, crowds directed chants at Hamas, a Sunni Arab group. "Shiites, Shiites," they shouted.

Across the Middle East, once antiquated words have sprung up in conversations about Shiites -- Safawis, for instance, drawn from the name of a Persian empire that brought Shiism to Iran. In Lebanon, posters have gone up in Sunni neighborhoods portraying leaders united by little other than their Sunni sectarian affiliation: Saddam Hussein, Yasser Arafat, Rafiq al-Hariri, the former Lebanese prime minister killed in a 2005 car bombing, and Sheik Ahmed Yassin, the leader of Hamas who was assassinated by Israel in 2004.

"You are in heaven," the poster reads, "and those who killed you will go to hell."

Iranian officials have repeatedly warned against the phenomenon, fearing it will curb their leverage in an Arab street that remains majority Sunni. Many in the Arab world watch its gathering force with a sense of helplessness.

"It's very bleak and it's very dangerous," said Dakhil, the Saudi writer. "We have a sectarian civil war in Iraq now and this is drawing sectarian lines through the region. This is the most important, the most dangerous ramification of the American war in Iraq."

Correspondent Scott Wilson in Jerusalem contributed to this report.