U.S. Vice President-elect Joe Biden met Iraq's Prime Minister Nuri al-Maliki in Baghdad on Tuesday to discuss withdrawing U.S. troops, seen as a major challenge for the incoming U.S. administration.

"Senator Joe Biden asserted the importance of cooperation ... to implement the foreign troop withdrawal agreement signed by the two countries," Maliki's office said, referring to a deal that requires U.S. troops leave Iraq by the end of 2011.

Biden arrived on Monday in Iraq, the statement from Maliki's office said.

As violence in Iraq falls to lows rarely seen since the 2003 U.S.-led invasion, U.S. forces are increasingly taking a back seat to Iraqi troops under a new bilateral security deal, which took effect at the start of the year.

Biden, a Delaware senator whose visit was in his capacity as long-time chairman of the Senate Foreign Relations Committee, held similar talks with other officials on Monday, including president Jalal Talabani and his deputy Adel Abdul Mahdi.

"Biden ... reiterated the United States's support for the process of restoring (Iraqi) sovereignty," the statement said.

Maliki was quoted as saying, "Iraq was threatened by ... sectarian war and its security forces were infiltrated by terrorists. But today ... it is on the right course."

The security pact calls for U.S. combat troops to leave Iraqi cities by the middle of this year and for all troops to withdraw by the end of 2011.

Negotiated by the outgoing Bush administration, it is compatible with President-elect Barack Obama's plan to withdraw combat forces by mid-2010.

Biden's arrival on Monday coincided with a wave of bombings across the capital that killed at least seven and wounded 30, a reminder of simmering unrest despite an end to rampant sectarian killing that nearly tipped Iraq into all-out civil war.

Biden's trip was the end of a tour including stops in Pakistan and Afghanistan, where Obama wants to send more troops as he pulls back from Iraq.

Biden is one of the few members of the U.S. Senate with a high profile in Iraq, where he is known as author of a 2006 plan to split it into self-ruled Sunni, Shi'ite and Kurdish enclaves.

That plan angered many Iraqi politicians, and was quietly put aside as violence ebbed. Biden voted for the 2003 invasion of Iraq but later became a harsh critic of the protracted war and the way President George W. Bush executed it.