KANILAN, Iraq - A U.S. airborne brigade in northern Iraq prepared yesterday to move south toward a ridge of hills northeast of Baghdad, backed by U.S. airpower, special operations forces, and tens of thousands of Iraqi Kurdish guerrillas, according to U.S. and opposition officials.

Combat forces from the 173d Airborne Brigade went out on armed patrols to probe for Iraqi forces in the direction of the oil-rich northern cities of Kirkuk and Mosul. But officials said the withdrawal of Iraqi Republican Guard divisions that had been guarding Mosul and Kirkuk until Tuesday appeared to have opened the way for a U.S.-led force to move toward Baghdad.

"We soon will be closing in on Baghdad from all directions, including the north," a senior administration official said.

Late yesterday, Mosul came under a ferocious U.S. air attack by B-52s.

On Tuesday, 400 Kurdish guerrillas, who have placed themselves under U.S. command, started a battle with Iraqi soldiers when they came under sniper attack.

Four hours later, with dawn coming, the first battle of the war in northern Iraq was over, with dozens of Iraqis dead and several hundred retreating toward Mosul. The lightly armed guerrillas, unassisted by U.S. forces, swarmed an Iraqi military post nine miles northeast of Mosul.

The Kurdish guerrillas took 33 prisoners, including an Iraqi colonel. One Kurdish fighter was killed.

The victorious guerrillas, known as peshmerga, belong to the Kurdish Democratic Party.

The new plan to send the peshmerga out of Kurd-controlled territory and south to the Hamrin Mountains, about 80 miles north of Baghdad, has two benefits, officials said. It puts pressure on Baghdad and reduces the danger that the Kurds and Turks will get embroiled in a squabble over Kirkuk, which the Kurds claim but which also has a large Turkmen population with ties to Turkey.

The Bush administration has won guarantees from the Kurds not to advance unilaterally on Kirkuk and Mosul for fear of angering neighboring Turkey. And Kurdish Democratic Party leader Massoud Barzani had promised that his men would not attack without U.S. permission.

But the commander of the Kurds who defeated Iraqi forces Tuesday said he could not wait for permission. "They shot at us, and we defended ourselves," Sarbaz Bapiri said. "We drove the Iraqis back, then later some American helicopters came."

Despite Tuesday's action, U.S. officials were pushing ahead to strengthen links with the Kurds.

Barzani and three other Iraqi opposition leaders are scheduled to meet today with an American special forces officer who is a liaison between U.S. Central Command and the opposition groups in northern Iraq. Kurdish peshmerga in the north are said to number 70,000.