Baghdad, Iraq ? U.S. military officials are preparing a major offensive against remaining strongholds of Saddam Hussein’s regime after a rocket-propelled grenade Thursday killed a U.S. soldier, the fifth American fatality in attacks this week.

Promising more raids, the U.S. command also said that soldiers descended on the Palestinian mission in Baghdad and detained diplomats and seized weapons and a manual on terrorism.

“The war has not ended,” said Lt. Gen. David McKiernan, chief of U.S. ground forces in Iraq.

Using harsh language not heard since the war was in full swing, top commanders vowed a hard-hitting backlash to clear out pockets of Baath Party and Republican Guard resistance.

The attack on a U.S. supply convoy 25 miles north of Baghdad on Thursday had the markings of similar incidents in recent days. The U.S. command did not identify the soldier killed when the grenade hit the trailing vehicle of the convoy but said the assailants were probably Saddam loyalists.

“We want to get rid of these scumbags,” U.S. Maj. Gen. James Mattis, commander of the 1st Marine Division said at a news conference in Baghdad.

McKiernan did not divulge details, but U.S. military officers said a troop buildup was in motion around the town of Fallujah and areas northwest of Baghdad where Saddam backers still run strong and anti-U.S. resistance remains fierce.

The American missions will concentrate on destroying militia posts, rounding up leading Baathists and collecting scores of weapons believed hidden in the region, U.S. military leaders said.

“Keep your eyes open. It will be a significant operation,” said one U.S. military spokesman.

Several U.S. soldiers interviewed in Baghdad said they were given orders Wednesday night to redeploy to the Fallujah area during the weekend. They had hoped to be sent home in early June, but the soldiers said several army brigades now faced at least two more months in Iraq.

Troops were told by their squad leaders to expect firefights and armed opposition. U.S. forces shot dead 16 Iraqis in Fallujah last month in a confrontation at a school where Americans had headquarters.

McKiernan said the United States would be targeting insurgents who were “combat” and not “criminal” types. He referred to the hotbeds for Saddam as a “battlefield.”

Though he doesn’t think the recent series of attacks on U.S. forces are tactically coordinated, McKiernan believes they have a common link. “I see it being orchestrated by enemies whose future has gone,” he said. “They were part of Saddam Hussein’s regime, they were tied to him. …. That is who we will close with and destroy.”

‘Welcomed with guns’

Two U.S. soldiers were killed Tuesday at a checkpoint outside Fallujah after Iraqis opened fire as their cars were being inspected for weapons. Some residents warned Thursday that U.S. troops would face a hard fight for control of the city of 200,000 and its environs.

They attribute anti-American hostilities to the U.S. military presence, which they view as an indignity and an occupation.

“More Americans will be welcomed with guns and fighters,” said one resident who identified himself as Ahmed Ali Mohammed at a market for guns and stolen cars near Fallujah. “The people will rise up against them.”

In Heet, north of Fallujah, tensions remained high after Iraqis reportedly rioted Wednesday during a search by Iraqi police and American soldiers for weapons of mass destruction.

A police station that was burned was still smoldering Thursday, visiting journalists said, and American soldiers wearing chemical suits and gas masks were stationed a few miles outside town. The U.S. military said it was investigating but would not provide further details.

In Baghdad, U.S. troops were more apparent on the streets. Tanks were stationed on several bridges and underpasses. Military checkpoints with Iraqi police were set up on highways and at intersections to look for arms.

At one checkpoint, soldiers and police collected 28 rocket-propelled grenades, two cartons of machine gun ammunition, an Iranian-made anti-personnel mine and roughly 50 anti-tank rounds, the military said.

U.S. forces have seized dozens of Iraqis in raids in recent days, but the operation against the Palestinians was apparently the first aimed at a diplomatic mission.

More than 40 U.S. soldiers and several armored vehicles raided the Palestinians’ headquarters Wednesday morning. They detained diplomats, drivers and gardeners. The forces had been scouring the neighborhood looking for culprits in Monday’s evening assault on a U.S. Humvee that killed one soldier and wounded three others.

Before the soldiers left early Thursday, they confiscated computer files, documents and even vases, said an embassy spokesman.

Seven Palestinians, including three with diplomatic status, and a Syrian were taken into custody, U.S. military officials said. U.S. forces confiscated “four AK-47s, seven grenades, one MP-5, four M-9s, a .48-caliber pistol and a book on terrorism,” McKiernan said.

Saddam was a strong backer of the Palestinian cause and sometimes funneled “reward money” to the families of Palestinian suicide bombers against Israel. Reporters found the Palestinian offices trashed Thursday after American soldiers left.

McKiernan said he offered no apologies.

“That happened in a part of Baghdad where we lost a soldier,” he said.