The alliance consists mainly of ethnic Tajiks, Uzbeks and Hazaras; the Pashtuns, the largest ethnic group, may not accept a new government unless they play a major role.
The opposition group agreed to participate in talks outside Afghanistan, but continues to resist U.S. and British pressure to accept international peacekeeping troops.
With the Taliban out of Kabul, Afghanistan's capital, there are growing concerns that the power vacuum could suck the country into the same anarchy that enabled the Taliban's rise.
In Kabul, there was music in the streets over the weekend, but also fear. Even as they celebrated the defeat of the Taliban, residents worried about a return to civil war and anarchy.
Four Western Journalists Killed
Today on the road from Jalalabad to Kabul, four Western journalists were killed — a reminder that the country has far to go before peace and stability.
The four were traveling as part a convoy of media vehicles when they were stopped in territory that was earlier believed to be safely under Northern Alliance control.
Near the town of Serobi, 35 miles east of Kabul, gunmen told their drivers not to go any further because there were snipers up on the hills shooting at cars as they were going by.
Ashiquallah, one of the drivers, told The Associated Press that a bus then came by and contradicted the gunmen's claims. But when the cars' drivers tried to speed away, the gunmen stopped them, he said.
The gunmen then ordered all the journalists out of the cars into the surrounding hills, and told their drivers to leave. When the journalists refused, they were beaten, Ashiquallah said. Then they were shot and killed
According to their employers, the journalists were Australian television cameraman Harry Burton and Azizullah Haidari, an Afghan photographer, both of Reuters; Maria Grazia Cutuli of Corriere della Sera; and Julio Fuentes of El Mundo.
Local militia have set out to recover the bodies, but turned back because the the ambush site was too dangerous, they said.
The militia commander in the area said he did not believe the gunmen were Taliban, but Ashiquallah said the gunmen told the journalists shortly before killing them, "'What, you think the Taliban are finished? We are still in power and we will have our revenge."'
British Troops Get Cold Shoulder
In other developments:
U.S. troops were joined by 85 British SAS commandos who arrived in Bagram on Friday, but the new arrivals were not greeted with welcome arms by the Northern Alliance, who seem to be growing mistrustful of the increased foreign presence in Afghanistan. Northern Alliance leaders argued that only 15 British soldiers were needed to help protect and maintain the air base. Britain has as many as 6,000 troops on standby to fly in.
Eight Western aid workers held for three months by the Taliban in Afghanistan were reunited with their families in Frankfurt, Germany, on Sunday. The workers had been detained since Aug. 3 on suspicion of preaching Christianity, a charge for which they could have faced the death penalty. The group was released when Northern Alliance forces took control of Kabul.
ABCNEWS' John McWethy, Jim Wooten and Don Dahler contributed to this report.