The commander of the U.S. war effort in Afghanistan, Gen. Tommy Franks, pledged Wednesday that "we will prevail" in clearing the Taliban out of Kunduz as new bombardment was reported outside the city, the Islamist militia's last bastion in the north.

"We need to complete the work in Kandahar ... and most importantly we need to complete the destruction of the Al Qaeda terrorist network," he told reporters at a U.S. base in Uzbekistan.

American warplanes reportedly targeted the Taliban home base of Kandahar in the south of Afghanistan early Wednesday.

Fox News has learned that more C-130 gunships — perhaps the most terrifying weapons in the U.S. arsenal — are being brought into the fray.

Meanwhile, the Taliban vowed on Wednesday to fight to the death to defend the few southern provinces still in their control.

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• Noose Tightens Around the Taliban

On the front lines of northern Afghanistan it was fast becoming a winter war. Outside Taliban-held Kunduz, shivering Northern Alliance soldiers thinned out from forward positions to huddle over fires in their foxholes.

Alliance Gen. Mohammed Daoud said thousands of Taliban have defected from Kunduz in recent days, and defectors' own accounts indicate at least hundreds have fled since Sunday. Dozens of Taliban fighters defected Tuesday.

Daoud said he was optimistic that he could finish brokering the surrender of Afghan Taliban at Kunduz, perhaps within a day.

The crew of a U.S. military helicopter has been safely recovered out of Afghanistan after a hard landing at about 1:10 p.m. EST Tuesday. Four crew members are receiving medical care for non-life-threatening injuries.

The cause of the accident is unknown, but it was not the result of hostile fire.

Earlier, an alliance spokesman, Attiq Ullah, said alliance forces would launch what would likely be a bloody assault to take the city if the Taliban did not surrender by Friday.

Rear Adm. John Stufflebeem, spokesman for the Pentagon, said that three-quarters of Afghanistan is now under anti-Taliban control. He said the situation at the only two major cities still held by the Taliban — Kunduz in the north and Kandahar in the south — was a "standoff."

On the front outside Kunduz, cold and rain all but halted fighting. U.S. B-52s and attack jets, heard but not seen through thick gray clouds, dropped far fewer bombs than in previous days.

Northern Alliance commander Fazal Jan said it was too cold for fighting now, and he was only waiting at the front near Kunduz for hundreds more expected Taliban defections.

A hard core of foreign fighters loyal to terrorist suspect Usama bin Laden — mostly Arabs, Pakistanis and Chechens — is determined to fight to the death and was preventing the Afghan Taliban fighters from surrendering Kunduz, refugees and defectors said.

The top U.N. envoy to Afghanistan, Lakhdar Brahimi, said Taliban commanders in Kunduz had passed a request through intermediaries for the United Nations to negotiate their surrender. But Brahimi said the world body didn't have the personnel on the ground to do so.

The Pentagon might halt some bombing while negotiations continue over Kunduz if the alliance requests it, Stufflebeem said. Defense Secretary Donald H. Rumsfeld has said he opposes any deal that would allow Taliban or foreign fighters in Kunduz to escape to do harm in another country later.

With the easing of the bombardment, refugee families from Kunduz straggled through the pass leading out of the front in the greatest numbers yet. Children walked wrapped in thin blankets as they paused in what was for some a two-day walk out of the city. Some stopped to rest, lighting fires of rice chaff to warm themselves.

In contrast to recent days, refugees said the foreign fighters did nothing to block their flight. Commander Jan said at least 700 had passed through the part of the front lines manned by his soldiers.

Taliban Retains Tenuous Grip on Kandahar 

Backed by U.S. bombardment, the Northern Alliance swept the Taliban out of northern Afghanistan last week and seized the Afghan capital of Kabul. The Taliban hold also fell apart in the south, where local leaders took control of many areas, but the militia held onto the southern city of Kandahar, their home base. 

Rumsfeld said the Taliban were under increasing pressure to release their grip on the city. 

"It is apparently at the moment still a standoff," he said of Kandahar.

Rumsfeld said the United States would not let Taliban leader Mullah Mohammed Omar escape from Kandahar, even if opposition leaders negotiated a deal for him to depart. 

The Associated Press contributed to this report.