US forces officially begin new Iraq mission: Biden

US Vice President Joe Biden said on Wednesday that American forces had begun a new mission in Iraq, a day after the US combat role in the war-torn country officially came to an end.

"Operation Iraqi Freedom is over but American engagement with Iraq will continue with the mission that began today, Operation New Dawn," Biden told US troops at Camp Victory, outside of Baghdad.

Biden was speaking hours after President Barack Obama announced in an Oval Office address that the US combat role, begun with the March 2003 invasion of Iraq, was now over, as uncertainty and violence continue to cloud the nation.

He said Iraqis had rejected violence, and called upon their leaders to form a new government, nearly six month after an indecisive general election.

Referring to Al-Qaeda, which has spearheaded a bloody insurgency in Iraq, Biden said: "The Iraqi people have rejected their ugly face of violence.

"I truly believe that the darkest days are now behind us," he said, pointing to Iraqis' "deeply felt desire to control their own lives and maintain their own security."

Turning to the continuing failure by Iraq's political factions to form a new government following the March 7 election, Biden said it was a sign that "politics has broken out in Iraq" but called on politicians to "place the national interest above their own."

"I strongly urge them to match the courage their citizens have shown by bringing this process to a close and forming a government," he said.

Speaking at a ceremony at which Lieutenant General Lloyd Austin formally replaced General Ray Odierno as new commander of US forces in Iraq, Biden also touched on the politician divisions caused in the United States by then president George W. Bush's decision to go to war.

"It is no secret that this war has divided Americans but they have never shrunk from the united support of the United States military," he said.

"Now is the time to put these differences behind us."

"More than a million American service members have deployed here ... and I am in awe of their accomplishment."

He also said: "Today is ... an important acknowledgement of the Iraqi losses in this conflict ... Tens of thousands of security forces and innocent civilians have been killed. Many times that number have been wounded and displaced."

With the end of combat operations, the remaining 49,700 US troops will focus on counterterrorism and training Iraqi forces.

While the "remaining troops are combat ready if needs be," Biden said their role would be to advise and assist Iraqi forces, support them in counter-terrorism operations and to protect US military and civilian personnel.

"We are ramping up our civilian and diplomatic effort to strengthen Iraqi sovereignty, stability and self-reliance," he said, adding that "our goal is not just a physically secure Iraq but an economically prosperous and stable one as well."

He spoke of enhancing the ties of trade and commerce and increasing cultural and educational exchanges, adding that "our diplomats will support Iraq's efforts to build strong ties with its neighbours and the wider world."