TORA BORA, Afghanistan - Afghan tribal fighters backed by tanks and U.S. warplanes mounted a heavy attack against Osama bin Laden's al-Qaida forces yesterday, seizing a key valley and pressing from three sides in a move to trap them on a rugged mountaintop near the Pakistani border.
Al-Qaida troops responded with rockets, artillery and mortars, shelling the tribal fighters' positions and the roads they are using to supply their front lines.
"Keep our fighters moving ahead," Afghan allied commander Haftagul, who goes by only one name, shouted into a hand-held radio to a commander several miles away at the front line. "Without occupying that peak we have no way to advance."
The valley captured yesterday leads to an underground complex of mountain caves where bin Laden may be hiding.
Haftagul said his men hoped to capture two high peaks that al-Qaida forces have fortified with mortars and machine guns, opening the way for a larger - and perhaps final - offensive. Pakistani troops reportedly have moved to seal off their border - which is only 20 miles from the fighting - to the rear of the al-Qaida positions.
"We want to occupy those peaks and encircle them," he said. "Then we will start our big attack. We hope to finish them off by Eid," or Dec. 16, the Muslim holiday marking the end of the holy month of Ramadan.
U.S. officials hailed the battlefield gains and said bin Laden is on the run but cautioned that it could take months to kill or capture him.
"It ain't over yet," Deputy Defense Secretary Paul D. Wolfowitz told reporters at a Pentagon briefing. "We've accomplished our one major objective, which is the defeat of the Taliban. ... Large numbers of al-Qaida terrorists are still at large.
"It's going to be a very long and difficult job."
The punishing U.S. air attacks in this area of eastern Afghanistan paused for part of the day to allow the Afghan fighters to move forward, but the strikes resumed after dark. U.S. officials described the bombings by B-52 and other warplanes as "intense."
The Pentagon also confirmed that it targeted a cave near Tora Bora on Sunday with a 15,000- pound bomb, known as a daisy cutter, after receiving information that the cave might have contained senior al-Qaida leaders, possibly including bin Laden.
Rear Adm. John D. Stufflebeem, deputy director of operations for the Joint Chiefs of Staff, said the daisy cutter closed the cave's entrance and, at the least, took a psychological toll on the al-Qaida forces in the area.
"This cave complex is literally on the sheer walls of a valley, and therefore the reverberation effect that goes up in those caves should have some kind of a negative effect," he said.
Meanwhile, U.S. Marines stepped up their search in the south for fugitive Taliban leader Mullah Mohammed Omar and other key figures of the Taliban and al-Qaida.
Traveling in helicopters and light armored vehicles, a contingent of the Marines moved closer to Kandahar from their Afghan base, Camp Rhino, yesterday to make it easier to block escape routes from the city.
Kandahar, the last stronghold of the Taliban militia that had shielded bin Laden, fell Friday to opposition forces allied with the United States.
More than a dozen helicopters dropped off Marines, food, water and weapons at a desert location near Kandahar where light armored vehicles and Humvee all-purpose vehicles had gathered since the morning.
Officers said the new staging area makes it easier for patrols to conduct manhunts. The vehicle patrols are armed with 50-caliber machine guns, anti-tank missiles and grenade launchers, and are supported by helicopters and warplanes.
"We're still looking for al-Qaida, and any Taliban that still have their weapons or don't drop them will die," Capt. Stewart Upton told reporters at Camp Rhino, the main base about 80 miles southwest of Kandahar. Marines above the rank of sergeant are carrying photographs of key al-Qaida and Taliban members to help in the task.
The Marines were active in the capital, Kabul, too.
Marines took control of the derelict U.S. Embassy to provide security for State Department officials who were assessing whether the building can be salvaged. Taliban mobs burned much of the annex buildings, and Taliban fighters hid there during the U.S.-led bombardments of the capital. The embassy has been closed since 1989.
About 12 Marines were visible on the roof, where they set up sandbags and a tripod-mounted machine gun; a few more were at the gate.
The United Nations announced Wednesday that Britain has accepted the task of leading and organizing a multinational force for Afghanistan. The Security Council is expected to approve the force by Friday, U.S. diplomats said yesterday.
But it is uncertain whether the security force can be in place by Dec. 22, when a new interim government is to take office in Kabul.
The U.S.-led war has undermined bin Laden's role as a terrorist leader and limited his ability to communicate and access support from his global network, Wolfowitz said yesterday.