Iraq's prime minister said Tuesday that U.S. and other foreign troops could begin handing over security to Iraqis in selected cities, although he opposes setting a timetable for the complete withdrawal of multinational forces.

Underscoring security concerns, a car bomb killed at least three people and wounded 15 Tuesday in the ethnically tense northern oil city of Kirkuk, police said. An American soldier died of injuries suffered in a land mine explosion south of the capital, the U.S. command said.

Prime Minister Ibrahim al-Jaafari (search) spoke to reporters alongside Deputy Secretary of State Robert Zoellick (search), who arrived Tuesday from Jordan, where he and Iraqi officials signed four economic agreements.

Al-Jaafari said he opposed such a timetable "when we are not ready" to assume responsibility for defending the country against the insurgents. However, al-Jaafari added that security in many of Iraq's 18 provinces has improved so that Iraqi forces could assume the burden of maintaining order in cities there.

"We can begin with the process of withdrawing multinational forces from these cities to outside the city as a first step that encourages setting a timetable for the withdrawal process," al-Jaafari said. "We don't want to be surprised by a decision to withdraw at a time when we are not ready."

He didn't specify which cities where he felt the redeployment could occur.

Zoellick's visit to Iraq had not been announced publicly. After meeting with al-Jaafari and others, Zoellick traveled to Hillah, about 60 miles south of Baghdad, where he met with Polish and other multinational troops.

The Defense Department wants to pull some of its 135,000 troops out of Iraq in 2006, partly because the mission is stretching the Army and Marine Corps perilously thin as casualties mount. U.S. commanders believe the presence of a large U.S. force is generating tacit support for anti-American violence.

However, wide areas of northern and southern Iraq are largely unaffected by the insurgency, which is concentrated in Baghdad and the Sunni Arab heartland of central Iraq.

Last weekend, The Mail on Sunday newspaper of London published a leaked British government memorandum showing that Britain is considering scaling back its troop presence from 8,500 to 3,000 by the middle of next year, saving an estimated $1 billion annually.

The memo, marked "Secret — U.K. Eyes Only," and signed by Britain's Defense Secretary John Reid, spoke of a "strong U.S. military desire for significant force reductions."

"Emerging U.S. plans assume that 14 out of 18 provinces could be handed over to Iraqi control by early 2006," which would see the multinational force cut from 176,000 to 66,000.

On Monday, British officials confirmed the authenticity of the document. Prime Minister Tony Blair's official spokesman, who speaks on customary condition of anonymity, said the memo merely confirms the government's long-standing plan to train Iraqi forces and gradually hand over security responsibility.

In Kirkuk (search), a car bomb went off in an industrial district as pedestrians were passing by, police Capt. Farhad Talabani said. Police rushing to the scene of the blast came under fire and three were wounded, one critically, police Col. Ahmed Hamawandi said.

Police said the bombing did not appear to have been a suicide attack, and no group claimed responsibility.

Kirkuk, 180 miles north of Baghdad, is located in one of the richest oil fields in the Middle East and is home to Arab, Kurdish and Turkomen communities, each vying for power there.

Iraqi troops, meanwhile, detonated about three tons of explosives found near oil fields in southern Iraq, a military spokesman said. The explosives, including 1,282 mines, 628 mortar rounds and 825 artillery shells, were discovered by Oil Protection Services who called the army to remove them, Capt. Firas al-Tamimi said.

Al-Tamimi said the explosives were believed to have been planted by Saddam Hussein's forces after the 1990 invasion of Kuwait — possibly to prevent the oil fields from falling to U.S.-led troops when they drove Iraqi troops from the emirate the following year..

The U.S. military said an American soldier has died of injuries he sustained when his patrol struck a land mine south of Baghdad.

The explosion occurred at around 9 a.m. Monday, the military said Tuesday. Three other soldiers were wounded in the attack near Mahmoudiya, which is about 20 miles south of Baghdad.

At least 1,756 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count. At least 1,352 died as a result of hostile action. The figures include five military civilians.

In Baghdad, gunmen assassinated a police colonel, Amir Mirza, in a market in the city's Wahda district, police said. The gunmen escaped.

Elsewhere, the country's largest Sunni political party condemned the deaths in police custody of up to 10 Sunni Arabs detained last weekend. The Iraqi Islamic Party said the men suffocated after being locked in a van for 14 hours in 105-degree temperatures.

In a statement Tuesday, the Iraqi Islamic Party denounced "this savage crime" and the "barbaric way citizens are being treated" in Iraq.