Although major combat in Iraq is over, the Pentagon's top general is still worried that Iraqi chemical or biological weapons could fall into the hands of terrorists.

The U.S. military so far has not confirmed finding any of the weapons of mass destruction the Bush administration says Iraq was hiding.

"We still have a lot of work to do in finding and securing weapons of mass destruction sites and making sure that those biological and chemical weapons don't fall in the hands of terrorists. That's still a possibility right now," Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said Tuesday night on CNN's Larry King Live program.

U.S. troops in the northern city of Mosul were involved in an armed confrontation Tuesday in which more than a half dozen people were killed, but precisely what happened was unclear, defense officials said. Iraqis said the Marines fired into a crowd of civilians, while defense officials said U.S. forces came under fire and shot back.

Lt. Cmdr. Charles Owens, a spokesman for U.S. Central Command, said officials were still trying to sort out what happened.

"We don't know anything about casualties, and I can't confirm anything about wounded," Owens said. "All we know for sure is that we didn't fire into a crowd of people."

The Pentagon raised the official U.S. death toll in the war to 123. Four Americans were missing, and none was listed as a POW.

Meanwhile, the U.S. military was pulling some forces away from the Iraq fight and working to set the stage for a new, democratic Iraqi government to take over.

Defense Secretary Donald H. Rumsfeld said a U.S.-led group charged with laying the foundation for a new civil administration, or interim authority, for Iraq will enter the Iraqi capital of Baghdad "once conditions on the ground permit."

He described the interim authority as a steppingstone to a new Iraqi government.

"It will be temporary; it will be large, involving Iraqis from all walks of life; and it will be open to participation by new leaders from across the country as they emerge from the shadow of Saddam Hussein's repression," Rumsfeld said.

U.S. military forces plan to snuff out any remnants of the Iraqi regime's Republican Guard or other Iraqi forces and take a closer look at clues to the whereabouts of four missing American troops, prisoners of war from the 1991 war and hidden Scud missiles or other illegal weapons, Rumsfeld told a Pentagon news conference.

"We'll continue these efforts until Saddam Hussein's regime has been removed from every corner of Iraq," the defense secretary said.

U.S. Marines controlled Tikrit, Saddam's hometown, after attacking it from the south, west and north and capturing a key Tigris River bridge in the center of the city about 90 miles north of Baghdad.

Fighting has ended in Qaim, a town near the Syrian border where Iraqi holdouts had been battling U.S. forces for about a week, military officials said. American troops still were negotiating with local leaders for control of the town, discussing issues such as whether and when a curfew would be imposed and what forces would police the town, U.S. officials said.

The only fighting of any consequence in Iraq on Tuesday was in two small towns near Tikrit, the officials said.

In the meantime, some U.S. forces in Iraq were being sent home while others arrived either to add new capabilities or to replace departing troops, Rumsfeld said. He confirmed that one ground force in line to deploy to Iraq had been told instead to stay home.

He would not identify the unit but others said it was the Army's 1st Cavalry Division from Fort Hood, Texas.

The size of the U.S. force remaining in Iraq as a postwar security force will depend in part, Rumsfeld said, on how willing other countries are to contribute peacekeeping troops.

Rumsfeld also said that it would take a while to decide the future arrangement of American forces in various Persian Gulf countries, many of which hosted U.S. troops that fought in Iraq.

"We have not made final decisions with respect to the footprint of the United States in that part of the world and won't for some months," he said.