Aiming for Saddam Hussein's seat of power, U.S.-led warplanes and helicopters attacked Republican Guard units defending Baghdad on Monday while ground troops advanced to within 50 miles of the Iraqi capital. President Bush put a $75 billion price tag on a down payment for the war.

The helicopter assault marked the first known engagement between forces in central Iraq, and many of the American craft were hit by Iraqi groundfire. One went down behind enemy lines -- the cause was unknown -- and the Pentagon said the two-person crew had been taken prisoner.

Five days into Operation Iraqi Freedom, resistance prevented American and British forces from securing the southern cities of Basra and An Nasiriyah and thwarted efforts to extinguish burning oil wells.

"These things are never easy," conceded British Prime Minister Tony Blair, on the day his country suffered its first combat casualty of the war. "There will be some difficult times ahead."

However, Blair said, the war "is going to plan despite the tragedies."

Saddam sought to rally his own country in a televised appearance. "Be patient, brothers, because God's victory will be ours soon," he said, appearing in full military garb and seeming more composed than in a taped appearance broadcast last week.

'Forces are closing in'

Despite Saddam's defiant pose, a military barracks in the northern part of the country was bombed, and Baghdad fell under renewed air attack by day and by night. Iraqis set up mortar positions south of the city and piled sandbags around government buildings and other strategic locations, in evident anticipation of a battle to come.

"Coalition forces are closing in on Baghdad," Maj. Gen. Stanley McChrystal told reporters at the Pentagon.

He said U.S. Apache helicopters attacked Saddam's Republican Guard forces arrayed around Baghdad while another official, speaking on condition of anonymity, said a "large portion" of the day's bombing runs were dedicated to hitting the same units.

Defense officials at the Pentagon said the Apaches encountered heavy groundfire during their assault on the Medina armored division. One official said many Apaches were hit by fire, but managed to kill about 10 Iraqi tanks before cutting off their attack.

The U.S. Air Force flew more than 1,500 sorties over Iraq on Monday. So far, 80 percent of the bombs and missiles used by the Air Force have been guided by lasers, radar, satellites or video cameras, a defense official said.

The Pentagon says the munitions are highly accurate, but Iraq claimed that 252 civilians had been killed Sunday, including 194 in Baghdad. It did not give any figures for military deaths.

Asked about ground forces, McChrystal said, "We have not gotten into direct firefights with Republican Guard forces."

That seemed a matter of not much time, though.

The Army's 3rd Infantry Division was within 50 miles of the capital, battling sandstorms more than Iraqi fire as it neared the approaches to Baghdad.

Heavy air protection

Some Iraqis waved or gave a thumbs-up as the convoy passed on its dash through southern Iraq, while others stood stoically.

The advance of long columns of thousands of vehicles was aided by heavy air protection that wiped out a column of Iraqi armor at one point and sent some of Saddam's outer defenses withdrawing toward the capital. The convoy passed bombed anti-aircraft guns, empty foxholes and berms dug for tanks that had been abandoned.

Bush, scheduled to confer in Washington later this week with Blair, also talked with Russian President Vladimir Putin by phone, complaining that Russia is selling anti-tank guided missiles, jamming devices and night-vision goggles to Iraq. National security adviser Condoleezza Rice visits U.N. Secretary-General Kofi Annan on Tuesday to discuss humanitarian issues.

Polls taken since the war began show growing support for the military campaign. But there were fresh anti-war protests across the United States and abroad. Police arrested more than 123 people in San Francisco, and at least 50 in Hartford, Conn.

In the world's first war with live broadcasts from the battlefield, news and images of American and British setbacks competed with pictures of military successes.

Iraqi television showed pictures of one American helicopter in a grassy field, men in Arab headdresses brandishing automatic rifles as they did a victory dance around the aircraft. Hours later, Iraqi television showed two men it said made up the crew.

"We have a two-man crew missing," confirmed Gen. Tommy Franks, the U.S. war commander. But he denied Iraqi reports that the craft had been shot down by farmers, and that two choppers had been lost.

Franks told reporters that 3,000 Iraqi prisoners had been taken. But he and other U.S. officials were more concerned with the fate of a handful of American POWs whose convoy was ambushed in the Iraqi desert over the weekend.

At the Pentagon, spokeswoman Torie Clark accused Iraqis of violating the rules of war by misusing white flags of surrender and other deceptions.

In London, the Ministry of Defense announced the first British combat death, a soldier who fell in fighting near Az Zubayr in southern Iraq, near the city of Basra.

Two other British troops were missing after their convoy was hit by continuing resistance in southern Iraq.

It was a fresh reminder that even in areas where American and British forces thought they had control, resistance continued to pop up.

"This is not a video game where everything is clear and neat and tidy," said British spokesman Lt. Col. Ronnie McCourt. "Some enemy who feel that they want to carry on fighting will inevitably do so."

Basra, Iraq's second-largest city, provided evidence of that, as Iraqis battled British forces on the outskirts of town. Commanders held off storming the city, hoping its Iraqi defenders would give up, but they have held firm.