Baghdad, Iraq ? U.S. investigators suspect the bombing of the U.N. headquarters in Baghdad was an inside job and are questioning Iraqi employees and guards, many of whom were linked to Saddam Hussein’s security service, a top American official said Friday.

Bernard Kerik, the former New York police commissioner who is working to re-establish an Iraqi police force, said the placement of the truck bomb and the timing of Tuesday’s attack had raised suspicions.

The truck was as close as it could have been to the office of Sergio Vieira de Mello, the top United Nations envoy and one of 23 people killed in the blast. The bomb went off as a high-level official meeting was in progress in the office.

“Would the security guards have access to that information? Would the people who work in that building for any other reason have access to it? How were the schedules distributed? They’re very basic parts of an investigation, and they’re nonaccusatory,” Kerik told The Associated Press.

Saying that the United States would “stay the course” in Iraq, President Bush blamed the continuing violence on foreigners.

“There is a foreign element moving into Iraq,” Bush said, calling them “al-Qaida type fighters” who hate freedom.

Bush said his administration was working with the United Nations to help bring peace the country and he predicted that U.S. allies would send reinforcements. “There will be more foreign troops in Iraq,” he said.

“Iraq is turning out to be a continuing battle in the war on terrorism,” Bush said.

Also Friday, the U.S. military announced the deaths of two soldiers. One serviceman was killed in action on Thursday in Hilla, 35 miles south of Baghdad, said Spc. Margo Doers.

The other died in a fire at a shooting range. The military did not say what caused the fire.

Kerik said some of the Iraqi personnel at the U.N. compound initially refused to cooperate with the bombing investigation and were being interrogated.