Associated Press writer

Edging closer to Iraq’s hard-core defenders, U.S. and British forces besieged the southern city of Basra on Saturday and rolled to within 150 miles of Baghdad. Diplomatic complications closed off the option of a heavy invasion from the north.

Allies boasted &uot;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 dusty dash 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.

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

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

&uot;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 &uot;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.