Iran's Shiite government helped end the clashes between Iraqi government troops and al-Sadr's Mahdi Army militia for the sake of Shiite unity, said a senior Iranian official who deals with Iraq.
"It is in Iran's best interests to see unity among Shiite factions," said the official, speaking on condition of anonymity because of the sensitivity of the issue.
Iraqi Prime Minister Nouri Al-Maliki heads a Shiite-dominated government in Iraq, but has clashed with other Shiite factions in the country, including the one led by al-Sadr.
Al-Maliki sparked clashes with al-Sadr's Mahdi Army over a week ago when he sent government troops to Basra to crack down on Shiite militias. The fighting eased last Sunday after al-Sadr ordered his men off the streets and called on the Iraqi government to end its attacks.
The Iranian government helped broker the truce during high-level talks in Iran's holy city of Qom with Shiite Iraqi officials and senior supporters of al-Sadr, said a prominent Iraqi party official based in Tehran.
"Iran played a mediating role and helped ease things a lot," said the Iraqi official, also speaking on condition of anonymity because of the sensitivity of the issue.
"Given its influence over al-Sadr, Iran convinced the Sadrists to stop fighting," he said.
U.S. officials in Baghdad have acknowledged an Iranian role in the talks but also accuse Iran of providing much of the weaponry used during the recent fighting, including rocket salvos against the U.S.-controlled Green Zone in Baghdad.
U.S. Ambassador Ryan Crocker said last Thursday that he wasn't sure the Iranians were instrumental in convincing al-Sadr to stop fighting "or whether they just didn't stop him from doing it."
The Iraqi government sent a three-member delegation that was headed by a prominent Shiite lawmaker close to al-Maliki, Ali Adeeb, and also included two of his Shiite colleagues, Hadi al-Amri and Qassem Sahlani, said the Iraqi official based in Tehran. The meetings in Qom also included representatives from Iran's elite Revolutionary Guards, he said.
Al-Sadr is believed to divide his time between Qom and Najaf, another Shiite holy city in Iraq 100 miles south of Baghdad. But Iranian government spokesman Gholam Hossein Elham denied al-Sadr's presence in Iran on Saturday, saying "this is what the occupying forces claim to divert the attention from what is going on in Iraq."
Iran's role in hammering out the peace deal is believed to have boosted Tehran's influence among Iraq's majority Shiite community.
U.S. and Iraqi authorities have insisted the Basra operation was not aimed at al-Sadr's powerful political movement but was aimed at ridding the streets of criminals and gunmen who had effectively ruled the city since 2005.
But al-Sadr's supporters believe the crackdown was aimed at weakening their movement before provincial elections this fall. Al-Sadr expects to score major electoral gains against Shiite parties that work with the Americans.