The deteriorating security situation may delay drafting the country's new constitution, a key step in the return to Iraqi sovereignty, a senior Iraqi official said Sunday.

Another U.S. soldier from the 1st Armored Division was killed late Saturday and wounded when their vehicle struck a land mine in Baghdad (search), the military said. A British soldier was injured in a land mine explosion in Basra, witnesses said.

Iraq's foreign minister, Hoshyar Zebari (search), told reporters that the U.S.-appointed Iraqi administration would submit a timetable to the U.N. Security Council for drafting a constitution and organizing national elections. The deadline was set by the Security Council in a resolution unanimously adopted last month.

"However, those timetables depend on the security situation, and if the security deteriorates, we will not be able to adhere to such commitments," Zebari said at a press conference with the Spanish foreign minister, Ana Palacio.

A new constitution would enable Iraqis to govern themselves and would hasten the day when American and other coalition forces could leave the country in the hands of a stable and democratically elected administration.

A major stumbling block for organizing a constitutional convention has been the question of choosing delegates. Key Shiite Muslim (searchclerics want the delegates to be chosen in a national election. Shiites comprise at least 60 percent of Iraq's 25 million people.

U.S. officials believe such an election would delay the selection. Other Iraqis prefer to see the delegates chosen by other methods, including having the Governing Council pick them from a list submitted by local and provincial leaders.

The security situation in Iraqi began deteriorating last month with an increase in American casualties after weeks of steady decline. Nearly half of all hostile deaths among American forces in Iraq since the end of major combat have taken place in the past five weeks.

On Saturday, Deputy Secretary of State Richard Armitage said the U.S. administration had been "sobered" by the escalation of violence but maintained that "we have a very solid plan to go out and get these people who are killing us and killing Iraqis."

"I'm pretty convinced ... that we will take this fight to the enemy," Armitage said after meeting with U.S. military and civilian authorities here.

In Tikrit, a U.S. official confirmed Sunday that an American major general was aboard a military helicopter was flying in formation with a Black Hawk that crashed there last week. The Black Hawk was apparently shot down by insurgents, although a U.S. investigation has made no final conclusions.

Maj. Josslyn Aberle, spokeswoman of the 4th Infantry Division, would not identify the general aboard the second helicopter, which landed safely. Six soldiers aboard the stricken helicopter died, including two from the Department of the Army headquarters at the Pentagon.

U.S. officials staged a massive show of American firepower during the night after the explosion, using jets, tanks and heavy weapons against abandoned buildings to discourage people from supporting the insurgents.