Iraq speech will not mark victory: Obama

"Our combat phase is over," Obama told American troops on a sprawling Texas military base before an Oval Office address to the nation to mark the end of combat in Iraq seven and a half years after the US-led invasion.

But the US commander-in-chief warned "there is still a lot of work to do" and he insisted his speech at 8:00 pm (0000 GMT) Tuesday would not be "a victory lap, it is not going to be self-congratulatory."

A major US troop pullout in past months has left less than 50,000 American soldiers in Iraq, but a surge in car bombings and shootings has left hundreds dead, and many remain fearful for the future.

In a television address to his people, Iraqi Prime Minister Nuri al-Maliki stressed the Iraqi military and police were now in charge, adding he was confident the last US forces would leave as planned at the end of 2011.

"This is a day that will remain in the memory of all Iraqis. Today, Iraq has become a sovereign and independent country," he said.

"As of today, our security forces will play the leading role in maintaining the security and defense of our country."

But Iraq has been left with no functioning government since March elections, with various attempts to form a coalition between rival groups failing to form a viable majority.

The White House on Tuesday urged Iraq to move forward with "a sense of urgency" on forming a new government after months of delay.

"We believe that government should be inclusive," Ben Rhodes, deputy national security advisor for strategic communications, told reporters.

US Defense Secretary Robert Gates also said Tuesday it was too early for victory parades, paying tribute to the 4,427 US troops killed in Iraq and the 34,268 wounded since the invasion to topple late dictator Saddam Hussein.

"I am not saying that all is, or will necessarily be, well in Iraq," Gates said in a speech in the Midwestern state of Wisconsin.

"This is not a time for premature victory parades or self-congratulation," Gates said, as he also focused on the war in Afghanistan where some 140,000 international troops are fighting a deadly Taliban insurgency.

Obama spoke in a mess hall before some 170 American troops, with a table poignantly set up with an empty chair, plate and a single rose to honor those killed in action.

"This table is empty. They are not with us today. Remember," said a notice next to the Table of Remembrance.

Obama, who opposed the 2003 invasion, also spoke earlier Tuesday with his predecessor, former president George W. Bush, who launched the war.

Since the start of the Iraq war, some 200,000 personnel from Fort Bliss have been deployed to the country, serving in every major phase of the war. During the initial invasion they were engaged in some of the heaviest fighting as they raced towards Baghdad.

Obama also warned of a "tough slog" ahead in Afghanistan. "We have seen casualties go up because we are taking the fight to Al-Qaeda and the Taliban," he said, with over 1,267 US troops killed since 2001 in Afghanistan.

White House spokesman Robert Gibbs said the change of mission in Iraq provided Americans with the opportunity to put behind them one of the most divisive periods in recent history.

"We can thank the men and women who made tremendous sacrifices. We can heal the wounds that were opened," he told ABC television.

White House officials said Obama would pay tribute to the bravery and sacrifice of American forces in his prime-time speech later Tuesday, and address the political divisions sown by the war.

However, a well-known Obama critic said the president, who opposed the so-called "surge" strategy in Iraq, should not be allowed to claim credit for improvements in security there.

"Some leaders who opposed, criticized, and fought tooth-and-nail to stop the surge strategy now proudly claim credit for the results," said House of Representatives Republican Minority Leader John Boehner, who underlined that credit for a more stable Iraq "belongs to our troops."