ISLAMABAD, Pakistan – After five years of military losses to the Taliban, Afghanistan's opposition has found a powerful new ally in the United States, which is threatening to attack Afghanistan to flush out Osama bin Laden.

The opposition controls barely 5 percent of Afghanistan, but is deeply familiar with the rugged terrain and would have invaluable intelligence for the United States. Many of its fighters were warriors in the U.S.-backed insurgency against the former Soviet Union.

"We have 15,000 people ready to fight. They are trained to fight the Taliban," A.G. Ravan Farhadi, the opposition's envoy in the United Nations, said earlier this week.

The United States has told the Taliban it must hand over bin Laden, whom they blame for last week's suicide attacks in New York and Washington, or face military retaliation.

The opposition could provide U.S. forces with information on locations and geography inside Afghanistan, and a U.S. special forces team could use opposition-held territory as a staging ground for any assault, analysts say.

According to diplomatic sources in Pakistan, the United States has already begun meeting with opposition leaders. It wasn't clear where the meetings were being held.

There were also reports that U.S. personnel were in northern Afghanistan meeting ex-President Burhanuddin Rabbani, who is headquartered in Faizabad, the capital of northeastern Badakhshan province, which borders Tajikistan in Central Asia.

Rabbani sent a letter to President George W. Bush soon after the attacks in the United States, "supporting a collective response," said Farhadi.

But the opposition is in a weakened state after the recent assassination of its charismatic leader, Ahmed Shah Massood. It blames bin Laden and the Taliban for the assassination.

Two days before last week's airborne assaults on the World Trade Center and the Pentagon, two men posing as television journalists died when the camera they were carrying stuffed with explosives blew up, killing Massood's spokesman and eventually Massood.

No one has been able to link the assassination and the terror attacks, but some opponents of the Taliban say it was intended to weaken the opposition ahead of an expected retaliatory assault by Washington against Afghanistan.

This presumes Massood's killers had prior knowledge of the U.S. terror attacks and expected Washing-ton to look for the perpetrators in Afghanistan.

Whether that proves to be true, the opposition that now wants to work with the United States is leaderless.

Massood was considered a skilled military strategist. Without him, the opposition is a weak collection of disparate groups, who fought each other bitterly when they ruled the Afghan capital of Kabul from 1992 until 1996, when the Taliban militia swept to power.

The opposition's deposed government still holds Afghanistan's seat in the United Nations and operates several embassies.

Coinciding with reports that the opposition and the Americans have met, were fresh Taliban offensives.

Fighter jets pounded opposition positions in northern Takhar province and at the battlefront north of the Afghan capital of Kabul earlier this week. The opposition initially reported that they had lost some high ground, which they said they later recaptured.

In recent years the opposition has been squeezed out of much of Afghanistan, holding pockets of ground in the north and central parts of the country.

One opposition leader who would be important to Washington is Rabbani's deputy prime minister, Abdul Rasul Sayyaf, who led the fundamentalist Islamic group Ittehad-e-Islami, or Islamic Unity.