Central Command said one soldier was killed and three were wounded in a blast in the town of Falluja, a hotbed of guerrilla violence west of Baghdad. Witnesses said a US convoy had driven over land mines planted on a road.

In Baghdad, an American soldier was killed in another attack on a convoy, the US military said.

The deaths bring to 64 the number of US soldiers killed in action, according to the latest Pentagon figures, since Bush declared major combat over on May 1.

The total number of US soldiers who have died in Iraq since the start of May now exceeds the number who lost their lives during the invasion and occupation of the country in March and April.

But Bush says efforts to secure Iraq will continue.

Thousands of troops from the 4th Infantry Division, based in Saddam's hometown of Tikrit, have launched a new operation to root out resistance in hostile Sunni Muslim territory to the north of Baghdad. Officers say Operation Ivy Needle will deprive Saddam and his top lieutenants of places to hide.

"That is our goal. After this, it is going to be difficult for him to hide, for his support network to operate properly," spokeswoman Major Josslyn Aberle said in Tikrit.

"Saddam is a master of hiding. If you look at his history, he had 30 years of practice, doubles running all over the place, secret places and so on."

Last week, Washington announced the capture of two of Saddam's most senior aides -- "Chemical Ali" Hassan al-Majid and former Vice President Taha Yassin Ramadan.

The operation began in earnest Tuesday when 24 suspected members of a criminal gang accused of attacking US forces were arrested by the 4th Infantry Division in the town of Khalis.