In western Iraq, 80 miles from the Syrian border, a car exploded at a checkpoint, killing three coalition soldiers, the driver and a pregnant woman who had emerged from the car screaming in fear, U.S. officials said. Central Command said it appeared to be a suicide attack, similar to the bombing at a checkpoint in south-central Iraq last week that killed four U.S. soldiers. 

Another soldier and an embedded reporter were killed when a Humvee went into a canal, said Navy Lt. Herlinda Rojas, a spokeswoman at Coalition Press Information Center in Kuwait City. No time, location or details about the fatal accident were provided. 

Though their troops were still searching underground bunkers for Iraqi holdouts, U.S. commanders announced that the Baghdad airport was under American control by mid-afternoon. It was renamed Baghdad International Airport instead of Saddam International Airport. 

"It is the gateway to the future of Iraq," said Brig. Gen. Vincent Brooks, who indicated the airport could be in use by U.S. forces within 36 hours. 

South of the capital, near the city of Kut, Marines said they had accepted the surrender of about 2,500 members of the Republican Guard - Iraq's best-trained forces, according to Navy Capt. Frank Thorp, a Central Command spokesman. 

Thorp said some of the Iraqis would be held as prisoners, while others who indicated they don't want to fight will be allowed to return home. Before surrendering, Thorp said, many of the Iraqis discarded uniforms, boots and helmets in the streets. 

Though Marines and infantrymen were converging by the thousands on the outskirts of Baghdad, U.S. officials, both on the front lines and at the Pentagon, suggested an all-out assault might not be their first option. 

Lt. Col. Scott Rutter, whose infantry battalion was helping secure the airport, said the approach of U.S. forces should send a message to the people of Baghdad. 

"We're here, and they can rise up and deal with the regime appropriately," he said. 

Similarly, President Bush's top military adviser, Joint Chiefs of Staff chairman Gen. Richard Myers, said U.S. troops forces might isolate Baghdad, rather than storming it, while work begins on forming an interim, post-Saddam government. Meyers estimated that Saddam's regime already has lost effective control of 45 percent of Iraq's territory. 

As Iraqis were cleared out of the airport, helicopter units of the 101st Airborne Division started to move in, presumably to use the facility as a base from which to strike at targets around Baghdad. 

"We're fighting in urban terrain now and to be effective in this terrain you need light infantry forces," Peabody said. "This is their forte and they provide us additional capabilities." 

Britain's defense secretary, Geoff Hoon, said the takeover was "a huge psychological blow to the regime." 

"It demonstrates to the regime and the people of Baghdad that we're there," Hoon said in a BBC radio interview. "We know they've been told by the leadership that there are no coalition forces anywhere near Baghdad. They will be able to see for themselves soon how untrue that is." 

In support of the ground troops, Navy warplanes from the carrier USS Kitty Hawk dropped satellite- and laser-guided bombs on hangars and a fuel depot at the airport, and struck a nearby military complex. 

Coalition forces also bombed Iraqi Air Force headquarters in central Baghdad early Friday, one of many air assaults on the smoke-filled capital. Blasts on the outskirts before dawn shook buildings in the city center. 

The air strikes came after the first widespread power outage of the war plunged Baghdad into darkness Thursday night and cut off running water in some neighborhoods. Though some bombs hit the city before the blackout, U.S. military officials said they had not targeted Baghdad's power grid. 

A sustained power outage would disrupt water supply and sewage, and create the threat of outbreaks of disease among the population of 5 million. Thanks to generators, however, the blackout did not affect hospitals that were crowded Friday with civilians and soldiers injured in fighting around the airport. 

U.S. and British officials say they do not know whether Saddam is alive and well, wounded or dead. 

Asked about Saddam by BBC radio, Iraqi Foreign Minister Naji Sabri replied, "He is well and the leadership is well and they are functioning as normal ... It is not our business to reply to rumors and lies." 

Some U.S. troops, inspecting an industrial site near Baghdad on Friday, found thousands of boxes of white powder, as well as nerve agent antidote and Arabic documents on how to engage in chemical warfare. However, a senior U.S. official said initial testing indicated the white powder was explosives, not chemical or biological weapons. 

Iraqi resistance to the American advance on Baghdad has been sporadic. U.S. Marines said they killed about 80 Iraqis in an intense battle Thursday in Kut, but in other areas Republican Guard soldiers dispersed or surrendered. 

U.S. soldiers of the 3rd Battalion, 7th Infantry captured four Republican Guardsmen south of Baghdad on Friday after a 30-second gunbattle over a vegetable patch. Two of the Iraqis were in uniform; two had changed into civilian clothes. 

The Marines' 1st Division was poised on the southeast outskirts of Baghdad after advancing along the Tigris River past abandoned Iraqi positions. Though temperatures headed into the 90s, Marines wore stifling chemical suits to protect against possible toxic attacks.