Khatami's request came when he called up the current chairman of the OIC, Malaysian prime minister Abdullah Ahmad Badawi.

He urged him "to call on members of OIC countries to meet in an emergency summit to try to find solutions to the deepening Iraqi crisis.

"The Iraqi interim government is in a difficult situation vis-à-vis the crisis in the holy city of Najaf, ...immediate action must be taken to end the escalating violence in that city," the Iranian president said.

US and Iraqi government forces are besieging rebel militia of cleric Moqtada Sadr in Najaf, a city sacred to Shia Muslims, who make up 90 percent of Iran's 66.5 million people are Shias.

On Thursday, Iranian Foreign Minister Kamal Kharazi called for an urgent meeting of Iraq's neighbours to help end the crisis there, marked by both Sunni and Shia insurgencies against the government and the US-led multinational force that support it.

"It is time for Iraq's neighbours to contribute to a resolution of the Iraq crisis," Kharazi was quoted as saying during a telephone conversation with his Jordanian counterpart, Marwan Moasher.

Four other countries neighbour Iraq, besides Iran and Jordan: Kuwait, Saudi Arabia, Syria and Turkey. Their foreign ministers have had a number of meetings since the US-led invasion that toppled the regime of Saddam Hussein in March last year.

Meanwhile, the United States has no conclusive evidence that radical Shiite cleric Moqtada Sadr has received arms from Iran, but refuses to rule out the possibility, a senior US official said Thursday.

"There are certainly those charges being made, but I guess we are hesitant to say definitively 'yes' or definitively 'no' because we just don't have conclusive evidence it's either validated or knocked down," a senior State Department official told reporters.

For more than two weeks, Sadr's Mehdi Army has been locked in heavy fighting with US-led Iraqi government forces on a mission to crush his militia in the holy city of Najaf.

Noting the "porous border" with Iran, the US official, speaking on condition of anonymity, said "it's certainly plausible" that Sadr was receiving weapons from Iran, but added that Washington could not be certain.

"I don't know if we've traced weapons in the hands of Mehdi people across the border to Iran," the official said. "There are plenty of weapons in Iraq you don't have to rely on Iran for them.

"Obviously they are getting their guns from somebody, but I don't think we are ready to say it is the Iranian government that's doing it."

On August 10, State Department deputy spokesman Adam Ereli said the United States was concerned by suggestions that Iran is involved in deadly unrest in Iraq's Shiite holy city of Najaf and maintained it was not in Tehran's interest to foment instability in its neighbor.