The Bush administration sees an opening with Iran in the recent flare-up of violence in Iraq, saying Tuesday that Shiite infighting may make Tehran think twice about undermining the U.S.-backed government in Baghdad.

At a congressional session marked by frequent questions about what the latest militia violence means, the top U.S. diplomat in Iraq said Iran is miscalculating, and he reissued an invitation to Iran for new talks with him about Iraq's security.

"I think one might look for a reconsideration in Tehran as to just where they want to go in Iraq," U.S. Ambassador Ryan Crocker said, adding that Iran's long-term goals "are best served by the success of this state and this government."

Crocker claimed that militias loyal to anti-American cleric Muqtada al-Sadr had alienated many Iraqis, and Iran's reputation suffered because Iraqis take it as a given that the militias are backed by Iran.

The Bush administration once resisted direct dealings with Iran, its longtime adversary, but agreed to limited meetings at the request of the U.S.-backed Iraqi government. Crocker and his predecessor as U.S. ambassador have held several meetings with Iranian counterparts, but Crocker has said the sessions produced no clear change in Iranian behavior.

The latest overture to renew those talks may indicate that the U.S. thinks the equation has changed.

"The government of Iraq is making efforts to see if it can schedule something, and if they can, we'll be there," Crocker said.

Crocker and Iraq military commander Gen. David Petraeus blamed Iran for funding, equipping and training Shiite militiamen that the U.S. military calls "special groups." Petraeus said most of the weaponry the militias used in recent clashes with Iraq and U.S. government forces came from Iran.

Al-Sadr ordered his fighters off the streets March 30 under a deal brokered in Iran. But the truce left the militia intact and armed and did not address the long-term threat.

Iran may have been a power-broker in ending most of the fighting, but that does not necessarily equal a tactical advantage, Petraeus told the Senate Armed Services Committee.

"Iran, at the end of the day, clearly played a role as an arbiter," Petraeus said. It's an open question "whether that strengthened them or also made them realize that their actions have been destructive in helping a country they want to succeed, presumably."

Iran stepped up its public support for Iraq's government on Tuesday, denouncing attacks on the Green Zone where it is based and praising Iraqi Prime Minister Nouri al-Maliki's crackdown against Shiite militias in the south.

Iran's comments highlighted how Tehran has spread its support among a range of Shiite factions in Iraq - including al-Maliki and members of his government.

Dozens of salvos poured into the Baghdad's fortified Green Zone after Iraqi forces opened the campaign last month against Shiite gangs in the southern city of Basra. Al-Sadr's Mahdi Army fought Iraqi police and soldiers to a stalemate in Basra and staged protests and attacks in Baghdad and elsewhere.

In Iraq's complicated politics, al-Maliki originally owed his job to support from al-Sadr, but the two are now at odds. Al-Maliki is a member of a rival Shiite political group.

The Sadrists believed the Basra crackdown was aimed at weakening their movement before fall elections in Iraq. They insisted al-Maliki was encouraged to move against them by their chief Shiite rivals - the Supreme Islamic Iraqi Council.

U.S. and Iraqi officials insist the crackdown is directed at criminal gangs and splinter groups supported by Iran.