President George W. Bush said during a surprise trip to Baghdad today he was encouraged by Iraq's new government but warned of difficult times ahead.
Mr Bush, on his second trip since the 2003 US invasion, was boosted by last week's killing of al-Qaeda in Iraq leader Abu Musab al-Zarqawi, but he was only cautiously optimistic.
US President George W. Bush with Iraqi Prime Minister Nuri al-Maliki during a meeting in Baghdad
"There are going to be tough days ahead, and more sacrifice for Americans, as well as Iraqis. But I come here - come away from here believing that the will is strong and the desire to meet the needs of the people is real and tangible," Mr Bush said.
Shortly after Mr Bush started meetings with Shia Prime Minister Nuri al-Maliki, al-Qaeda's new leader in Iraq warned that Americans and their Iraqi allies would not be safe in their fortified compounds, according to an Internet statement.
"The day of vengeance is near and your strong towers in the Green Zone will not protect you," said the statement posted on a Islamic militant Web site and signed by Abu Hamza al-Muhajir.
Mr Bush said the US military would remain on the offensive. "We will continue to hunt down people like Mr Zarqawi, and bring them to justice," he said to the applause of US troops.
Bombings that killed at 14 people in the city of Kirkuk were seen as a bid by al-Qaeda to show it was still going strong.
"Our swords are poised above your necks," said a statement signed by Zarqawi's successor, the little-known Abu Hamza al-Muhajir, on a website often used by Islamic militants.
Security concerns meant Mr Bush's journey was top secret. Only Vice President Dick Cheney, Defense Secretary Donald Rumsfeld and Secretary of State Condoleezza Rice were aware he had slipped away from Camp David abruptly last night.
Mr Bush spent several hours in Baghdad before returning to Washington.
Aides said he was in the cockpit of Air Force One when it landed in the Iraqi capital with a sharp bank and quick landing. He then took an eight-minute helicopter ride in searing heat to the "Green Zone" for talks with the Iraqi cabinet and US commander in Iraq General George Casey at the US embassy.
Mr Bush's meeting with the Iraqi cabinet was connected by video to Camp David, where Mr Cheney, Mr Rumsfeld and Ms Rice remained.
The president told Mr Maliki and his ministers they carried heavy responsibilities but that America stood by them.
"I have come to not only look you in the eye; I've also come to tell you that when America gives its word, it will keep its word," Mr Bush said.
Mr Maliki said postwar Iraq's first full time government was determined to defeat the insurgents. "God willing all the suffering will be over, all the soldiers will return to their countries with our gratitude, for what they have offered, the sacrifices," said the former exile.
The US death toll in Iraq since the March 2003 invasion is approaching 2,500, and tens of thousands of Iraqis have died. US public unease with the war is growing in a congressional election year and Mr Bush faces calls to set a timetable for withdrawal of some 130,000 US troops.
In a letter to the United Nations Security Council circulated, Iraq said its forces were not yet ready.
In one of the Kirkuk attacks, a car bomb exploded outside the house of a senior police officer, seriously wounding him and killing one of his bodyguards, police said.
As police and US forces gathered in the area, a roadside bomb exploded, killing 10 civilians, in a common tactic by Sunni Arab insurgents bent on toppling the Shia-led government.
A defence ministry official said more than 40,000 Iraqi and US forces would mount a crackdown in Baghdad tomorrow, in what would be one of the biggest operations since the 2003 war.