(Adds comments from U.S. ambassador to Iraq)
TEHRAN, April 4 (Reuters) - Iran helped end last week's fighting between Iraqi government troops and a Shi'ite militia in Iraq's oil-rich south, an adviser to a leading Iraqi Shi'ite politician was quoted as saying on Friday.
The comments by Mohsen Hakim, whose father Abdul Aziz al-Hakim heads the Supreme Islamic Iraqi Council, underlined Shi'ite Iran's growing influence in Iraq after the U.S.-led overthrow of Sunni Arab strongman Saddam Hussein in 2003.
Washington accuses Iran of stoking violence in its neighbour by funding, training and equipping Iraqi militants. Iran denies this and blames the presence of U.S. troops for the bloodshed.
Mohsen Hakim told Iran's Mehr News Agency an Iraqi delegation led by a prominent Shi'ite lawmaker held talks with Iranian officials during a visit to Iran last Friday.
Two days later, fiery anti-U.S. Shi'ite cleric Moqtada al-Sadr announced a truce to end six days of clashes with Iraqi and U.S. troops in the southern city of Basra that spread through southern Iraq and Baghdad.
U.S. officials say Sadr is currently in Iran.
"Tehran, by using its positive influence on the Iraqi nation, paved the way for the return of peace to Iraq and the new situation is the result of Iran's efforts," Hakim was quoted as saying, without giving further details.
Members of the Iraqi delegation have confirmed to Reuters they went to Iran just before Sadr announced the ceasefire but have declined to give details on any role Iran played.
Prime Minister Nuri al-Maliki's crackdown on militias in Basra exposed a deep rift among Iraq's majority Shi'ites.
The Supreme Council is a key backer of Maliki but a bitter rival of Sadr's movement. The two groups are competing for power in Shi'ite southern Iraq, home to most of Iraq's oil reserves.
The Sadrists, who helped install Maliki in power in 2006 but broke with the government last year, have accused Supreme Council followers of infiltrating the security forces and attacking them.
The U.S. ambassador to Iraq, Ryan Crocker, told foreign reporters on Thursday he was not aware of what role, if any, Iran had played in Sadr's decision.
He drew attention instead to the hail of rockets and mortars fired at the Green Zone government and diplomatic compound in Baghdad during the crisis that he said were made in Iran.
"Let's start with the Iranian involvement not in ending it, but maybe in beginning it," he said.
U.S. officials say rogue members of Sadr's militia get support and weapons from Iran.
"We got the tail fins of what was dropping on us ... This was quite literally made in Iran. All of this stuff was out of Iran and a lot of it manufactured in 2007," Crocker added.
Last week's fighting, in which several hundred people were killed in southern Iraq and Baghdad, served as a reminder of the instability in Iraq after months of security improvements. (Reporting by Zahra Hosseinian in Tehran and Dean Yates in Baghdad; Writing by Fredrik Dahl; Editing by Giles Elgood)
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