Advancing in a dusty dash toward Iraq's hard-core defenders, U.S. forces rolled to within 150 miles of Baghdad and besieged the southern city of Basra. A grenade attack Sunday at a base camp in Kuwait wounded 14 American soldiers.

Allies boasted ''the instruments of tyranny are collapsing,'' and so, from all appearances, was the will to fight among thousands in the regular Iraqi army. Still, resistance in some areas was fierce.

On the outskirts of Basra, a city of 1.3 million where Saddam Hussein's tough security fighters were thought to be lodged, allies captured the airport in a gunbattle and took a bridge.

U.S. forces crossed the Euphrates River and were halfway to Baghdad, two days after spilling from Kuwait in a sprint that has secured strategic oil fields, a seaport and towns.

Near Basra, Cobra attack helicopters, attack jets, tanks and 155 mm howitzers fought ahead of the troops to clear Highway 80. The road was nicknamed Highway of Death during the 1991 Gulf War because of an American air assault so devastating and graphic it even gave U.S. officials pause.

Officials said 1,000 to 2,000 Iraqi soldiers were in allied custody and many others gave up the fight. But six divisions of the Republican Guard, Saddam's best and most loyal soldiers, were still in the way.

''So we must remain prepared for potentially tough fights as we move forward,'' Gen. Stanley McChrystal told a Pentagon briefing. ''There's a long way to go.''

There was danger away from the front lines, as well. In northern Kuwait, troops in a tent at a 101st Airborne Division camp were attacked with grenades, wounding 13 soldiers. A U.S. soldier was detained as a suspect.

At Camp New York, another staging camp in northern Kuwait, a Patriot missile hit an incoming missile, a military official in Kuwait said. There were no reports of injuries.

The fate of the Saddam remained unknown to the U.S. and British officials trying to kill him.

''Actually, I don't know if he's alive or not,'' said U.S. Gen. Tommy Franks, the war commander.

Saddam was shown on Iraqi TV again Saturday but there was no telling when the tape was made.

U.S. officials had no new, credible intelligence showing whether he had survived assaults on his compounds, or whether he might have been wounded.

A U.S. official, speaking on condition of anonymity, said another senior Iraqi leader was known to be alive and might be running some of Iraq's defenses: Saddam's cousin Ali Hassan al-Majid al-Tikriti, known to his enemies as ''Chemical Ali'' for his role in a chemical-weapons attack on Kurds in 1988.

Any thought the allies would limit air attacks to the cover of darkness vanished in the smoky sunlight Saturday.

Twenty huge columns of smoke rose along Baghdad's southern horizon Saturday afternoon and intermittent explosions were heard through the capital.

When darkness did fall, the intensity picked up. Strong blasts rocked the capital. Warplanes were heard overhead once again. The attacks eased as the night wore on, but a new round of explosions rattled the city early Sunday.

Six Britons and a U.S. Navy officer died Saturday when two Royal Navy helicopters collided over the Persian Gulf. On Friday, two U.S. Marines were killed in combat and a helicopter crash left eight British and four U.S. Marines dead.

Sickened by the escalation of a campaign they already opposed, demonstrators rallied worldwide to give voice to their rage. Even so, crowds were smaller than before the conflict.

''We don't want to see more innocent people die,'' said Susan Sonz, who joined 100,000 in New York City. An estimated 200,000 rallied in London. Tens of thousands marched in France, some holding rainbow-hued peace flags and others shouting ''Bush, murderer.''

Italian protests were marked by smashed windows in Milan and vandalized gas stations in Rome.