* End of U.S. combat mission a milestone in war
* Biden to talk to leaders about political impasse
(Adds rockets in Green Zone, U.S. general quote)
BAGHDAD, Aug 30 (Reuters) - U.S. Vice President Joe Biden flew into Iraq on Monday to assure Iraqis the United States is not abandoning them as it stops combat operations, a milestone in the 7-1/2 year war the Obama administration is trying to end.
Biden will hold talks with Iraqi leaders amid a political deadlock almost six months after an inconclusive election in March over forming the next government, the White House said.
The impasse has turned the Aug. 31 end of the U.S. combat mission, and accompanying reduction in the U.S. troop levels in Iraq to 50,000, into something of a gamble as political tensions simmer and attacks by insurgents persist.
"In short, we are determined to build a long-term partnership with the government of Iraq and with the Iraqi people, but to build a partnership you need a partner," Tony Blinken, Biden's national security adviser, said.
"And so the vice president I'm sure will also in his meetings talk about the government formation process when he meets Iraq's leaders," Blinken told reporters in Baghdad.
Meeting the Aug. 31 deadline allows President Barack Obama to say he is fulfilling a pledge to war-weary U.S. voters to end the war launched by his predecessor as Obama's fellow Democrats seek to retain control of Congress in elections in November.
The 50,000 U.S. soldiers remaining up to a full U.S. withdrawal next year will train and assist Iraqi security forces as they battle Sunni Islamist insurgents and counter Shi'ite militia. They still represent a formidable force.
Overall violence in Iraq has fallen sharply since the peak in 2006/07 of the sectarian slaughter unleashed after the 2003 U.S.-led invasion, but levels of violence remain high.
Two rockets or mortar rounds landed late on Monday in Baghdad's fortified Green Zone where government offices and embassies, including that of the United States, are located, Interior Ministry and police sources said. There was no immediate information on casualties or if the attack had been close to the U.S. embassy.
About 60 rocket or mortar rounds were fired at the Green Zone or Baghdad's airport in the past two months, Brig. Gen. Ralph Baker, one of three deputy commanding generals for U.S. forces in central Iraq, said on Monday.
"We have seen an increase in indirect fire in Baghdad over the last two months... It has gone up substantially," he told reporters.
Suspected al Qaeda-linked insurgents have launched a number of assaults ahead of the change in U.S. military mission, seeking to undermine confidence in Iraqi police and soldiers.
A suicide bomber killed 57 at an army recruitment centre on Aug. 17 and more than 60 people were killed when suicide car bombers attacked police stations on Aug. 25.
U.S. and Iraqi officials have said the insurgents also are trying to stir sectarian tensions amid the political vacuum.
POINT MAN FOR IRAQ
A Sunni-backed cross-sectarian alliance headed by ex-premier Iyad Allawi won two more seats in the 325-seat parliament in the March 7 vote than Prime Minister Nuri al-Maliki's Shi'ite-led bloc, but neither has the majority needed to govern.
Biden, Obama's point man for Iraq, has flown into Baghdad five times since becoming vice president, usually when political squabbling threatens to escalate to crisis levels.
U.S. officials have stressed they do not think they have a right to interfere too directly in Iraq's fledgling democracy.
"We neither want to, nor can really, play any real role in this. We're not the CPA," new U.S. ambassador James Jeffrey said last week, referring to the U.S.-appointed Coalition Provisional Authority that ran Iraq like a colony after the invasion.
Additional reporting by Thaier al-Sudani and Serena Chaudhry; Writing by Michael Christie; Editing by Michael Roddy
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