* Iran not having as much impact as it wants
* Recent attacks blamed on al Qaeda
BAGHDAD, Aug 26 The new U.S. ambassador to Iraq said on Thursday he believed groups backed by Iran were responsible for a quarter of U.S. casualties in the Iraq war but that Tehran was not as influential in Iraq as thought.
More than 4,400 U.S. soldiers have been killed since the 2003 U.S.-led invasion, battling Shi'ite militia the U.S. military has long said were armed, funded and trained by Iran, and Sunni Islamist insurgents.
The U.S. military will formally end its combat operations in Iraq on Aug. 31 as President Barack Obama seeks to fulfil a promise to U.S. voters to end the war, despite continuing insecurity and political instability in Iraq.
Ambassador James Jeffrey said Tehran had not been able to dictate the outcome of Iraqi coalition talks after an election in March, despite efforts and widespread beliefs that Shi'ite Iran gained unprecedented influence in Iraq after the invasion.
The ousting of Sunni dictator Saddam Hussein propelled Iraq's previously oppressed Shi'ite majority into power.
"My own estimate, based just upon a gut feeling, is that up to a quarter of the American casualties and some of the more horrific incidents in which Americans were kidnapped ... can be traced without doubt to these Iranian groups," Jeffrey said.
He said Iran has sought to use Iraqi proxies to destabilise its neighbour and make it inhospitable for foreign forces.
"But I don't see any long-term impact that it, however awful, has had on the development of politics and society here," Jeffrey told Western reporters. "I believe ... that Iraqis are Iraqi patriots, that they do not want to be dominated or dictated to by anybody, not the United States, not Iran, not any of their other neighbours."
Coalition talks since the inconclusive election have failed to produce a government, despite early agreement between Iraq's main Shi'ite blocs to form a parliamentary alliance and efforts by Tehran to encourage Iraq's Shi'ite parties to unite.
Suspected Sunni Islamist insurgents have meanwhile tried to exploit the political impasse through a steady stream of suicide bombings, car bombs and assassinations since the vote.
They launched a nationwide assault on police on Wednesday in which 62 people died in an apparent campaign to discredit the Iraqi security forces as the U.S. combat mission ends and U.S. troop numbers fall below 50,000.
Jeffrey said the United States was very concerned about the political deadlock, and he blamed Wednesday's attacks on al Qaeda-linked groups.
He said that while significant, the attacks did not change the fact that overall security incidents in Iraq had fallen sharply over the past two years, adding that the end of combat operations did not mean the United States was disengaging.
"The point that we are trying to make ... is that we are not abandoning Iraq. We are not even leaving Iraq," he said.
"We are simply, because the situation -- particularly the security situation and in general the political and economic evolution in this country, as it should when things go fairly well -- allows us to withdraw our ground military presence." (Reporting by Michael Christie; Editing by Jon Hemming)