Four weeks into the bombing of Afghanistan, U.S. Defense Secretary Donald Rumsfeld said Sunday that the attacks had weakened the Taliban's hold on the country and the U.S. is making "measurable progress" in the war on terrorism.

"The Taliban is not really functioning as a government as such," said Rumsfeld, who was on a four-day, five-nation trip to Central Asia to cement support for the U.S.-led campaign. "They are not making major military moves. They are pretty much in static positions."

In the United States, Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said that more Special Forces troops had been deployed in Afghanistan in the past few days. They will work with rebel forces in targeting Taliban troops and members of Osama bin Laden's al-Qaida terrorism network, he said.

"The more teams we get on the ground, the more effectively we'll bring air power to bear on the Taliban lines," Myers said on NBC's "Meet the Press" program.

The U.S. may be able to use air bases in Tajikistan for the helicopter-borne Special Forces and to launch bombing raids against the Taliban. Tajikistan and the United States reportedly have reached a tentative agreement on military cooperation that could lead to U.S. air strikes from bases in the nation neighboring Afghanistan.

A U.S. inspection team has arrived there to examine three former Soviet bases to see whether they still are usable.

Myers and Rumsfeld spoke as American fighters and B-52 bombers pummeled four key cities in northern Afghanistan for seven hours in an apparent attempt to lay the groundwork for an offensive by the rebel Northern Alliance. But an alliance push toward the strategic city of Mazar-e Sharif was reported to be faltering hours after it began.

Despite reports that a major rebel offensive could be imminent, U.S. officials cautioned that might not be the case.

"I don't know that I'd want to characterize the situation right now as saying we should be forward in the saddle and waiting for ground operations by the Northern Alliance, or a major effort by the Northern Alliance, in the next few days," Gen. Tommy Franks, head of the U.S. Central Command, said on ABC's "This Week."

Asked if he would rule out a major deployment of ground forces against the Taliban, Franks replied, "Absolutely not."

Some officials have expressed disappointment in the Northern Alliance's failure to take territory from the Taliban despite the intensity of the U.S. bombing campaign. But Myers said that despite the lack of visible progress and the onset of winter, the campaign is going as expected.

"The Taliban are on their heels," Myers said. "We have the initiative. ... I'd rather be in my position than theirs right now."

Myers said the U.S. would continue to supply the rebels through the winter. "We're settling in for the long haul," he said.

Preparing for second phase

After four weeks of bombing, the U.S. military is girding itself for the second and most complex phase of its campaign. The first phase relied exclusively on air strikes. The second is supposed to make considerable use of U.S., and eventually British, special operations forces.

The number of U.S. troops in Afghanistan is believed to be 100 to 200 and probably includes Green Berets, Army commandos who specialize in advising foreign forces. Rumsfeld said last week that he hoped to at least triple the number of Special Forces troops in the country but that efforts to deploy them had been stymied by bad weather and, in one case, ground fire.

Northern Alliance spokesmen said they had launched a three-pronged offensive south of Mazar-e Sharif in a province bordering Uzbekistan, beginning the attack after the U.S. softened Taliban positions with heavy bombing. But within hours, the rebels said one of the opposition columns had bogged down.

Nonetheless, Rumsfeld told reporters in Uzbekistan that the war is going well.

"We believe we're proceeding at a pace that is showing measurable progress," Rumsfeld said. Although the Taliban still packs a military punch, he said, it has been crippled by the raids.