Leaders of the rebel Northern Alliance prepared to enter Kabul early Tuesday, hours after the ruling Taliban government apparently deserted the Afghanistan capital.

According to witnesses, a rebel advance force entered the city without a fight. The Taliban had left under cover of darkness.

By midmorning, a traffic jam stretched nearly a mile from the city limits, as hundreds of city dwellers streamed toward the rebel forces.

"I want to come and appreciate these soldiers," said one city resident, Abdulla, 23. "All the people are happy. ... Right now there is nobody in control of the city."

Rebel security forces were gathering outside the city to enter before the soldiers.

Gen. Haji Alamas said the Northern Alliance troops would first secure the entrances to the city and then enter in force. "We don't want our soldiers to enter yet," he said. "We are feeling happy that we will capture the center of Afghanistan."

At least six Taliban defenders lay dead on the road to the capital.

"We have taken Kabul!" an opposition fighter shouted on a street of the capital, 38 days after the United States launched a military campaign against the Taliban and Al Qaeda, the terrorist network run by Osama bin Laden.

U.S. officials cautioned that the Taliban's evacuation may be far from complete. It also was unclear whether the Taliban forces may have been regrouping for a counterattack.

The absence of an established government in Kabul heightened the sense of political instability in the war-ravaged nation and generated urgent discussions in the international community about quickly installing an interim government.

Secretary of State Colin Powell said Monday that Taliban forces were close to collapse across much of the northern part of the country and that an international "coalition of the willing," led by soldiers of Muslim nations, may be needed to secure Kabul in preparation for a new ruling government.

The main concern among Afghanistan's neighbors and backers of the U.S.-led anti-terrorism campaign is that the rebel Northern Alliance, representing minority Afghan tribes of Tajiks and Uzbeks, would not be able to effectively rule the ethnically fractious country and prevent further chaos. Reports of summary executions of captured Taliban soldiers by the rebels further increased the anxieties.

The rebels announced Monday that they had captured the western cities of Herat and Zaranj, near the Iranian border, while reports from Kabul indicated that the Taliban had pulled out of the capital. As they left, the Taliban took eight foreign aid workers, including two Americans, held on charges of spreading Christianity, witnesses said.

In three days of fighting, the territory claimed by the rebels has grown from 10 percent of Afghanistan to half of the country.

"As things are moving very fast, we need to bring the political aspects in line with the military development on the ground," UN Secretary General Kofi Annan said, urging Afghan politicians to meet quickly and begin negotiations to form a coalition government to replace the Taliban, which has ruled most of the nation since 1996.

"We have always been aware that when you get into these kinds of operations, things can move very fast, and sometimes can get stuck," Annan said in New York. "We have to be able to move quickly, and we have to be flexible."

The sense of urgency was underscored at the UN when Powell and Iranian Foreign Minister Kamal Kharrazi shook hands in a gesture of support for the effort to install a new Afghan government. The U.S. broke off diplomatic relations with Iran in 1979 following the Iranian hostage crisis.

Afghanistan's former king, Mohammed Zahir Shah, viewed as a potential rallying figure for a new government, said in an interview with the BBC that he hoped his nation would emerge united from years of war after having been turned into "a den of terrorists" by the Taliban.

Under Taliban rule, Afghanistan has been a haven for Saudi exile bin Laden and his Al Qaeda network, considered by Western officials to be responsible for the Sept. 11 terrorist attacks on the World Trade Center and the Pentagon. President Bush launched the bombing campaign against the Taliban on Oct. 7 after it refused to hand over bin Laden.

From stalemate to retreat

Only a week ago the U.S.-led military campaign was thought to be approaching a stalemate with the stubborn Taliban fighters, who clung tenaciously to the strategic northern city of Mazar-e Sharif and repeatedly fended off challenges from the loosely organized rebels. That changed Friday with the fall of Mazar-e Sharif after days of concentrated bombing by U.S. warplanes and repeated ground offensives by the rebels.

Northern Alliance commanders said Monday that they were pushing toward Kunduz, the last Taliban-held city in the north.

"It's clear the Taliban are unraveling, but they are not beaten yet or Al Qaeda yet hunted down," British Prime Minister Tony Blair said in London. "We must continue until they are."

U.S. and British military advisers have helped coordinate efforts between U.S. bombers and rebel forces, and have played a key role in the Northern Alliance's success.

Even with the apparent power shift, though, the situation in Afghanistan is one of tenuous stability, and gains by the rebels may only be a prelude to a lengthy and bloody struggle as the Taliban dig in to defend their southern base and the spiritual stronghold of Kandahar.

On Monday, dozens of Taliban tanks and armored personnel carriers were seen racing out of Kabul as darkness fell. The rebels said they had broken through the Taliban front lines with the support of U.S. warplanes, which have been bombing Taliban positions and helping coordinate rebel strikes.

Emboldened by the capture of Mazar-e Sharif, the rebels also claimed to have control of Taloqan and Herat. Late in the day, an alliance warlord claimed to have captured Zaranj, in southwestern Afghanistan near the border of Iran.

The rebel gains created a ragged front stretching from the outskirts of Kabul and west to Herat and Zaranj. U.S. officials repeatedly have urged the Northern Alliance to delay moving into the capital until a new government can be inserted. But they have acknowledged that they cannot control the movements of the rebels.

"The United States has been fighting the terrorists since Sept. 11. We have been fighting them for seven years," said Saed Ahmad, a tank commander for the Northern Alliance. "We have many martyred comrades and we want revenge."

Ahmad also promised that the opposition would take Kabul, even though the U.S. and many of its coalition partners want the fighters to stay out for now.

"Whether the United States wants it or not, we will take Kabul," he said Monday.

The Taliban exit from Kabul came in the predawn hours of Tuesday, as Northern Alliance forces reportedly were moving into the city in pickups, preparing for a daylight attack. But when the sun rose on the capital, the Taliban forces were gone, witnesses said.

Northern Alliance forces took control of government buildings in Kabul and, according to witnesses, were pursuing the Taliban to the west.

While this change of events of the past four days is good news for the anti-terrorism effort, it does not alter the assessment of top Pentagon officials that Kabul, which changed hands in 1992 and 1996, is less important than the southern Afghan city of Kandahar, home base of the Taliban.

In an effort to put more pressure on the Taliban, the Pentagon said Monday that it has decided to put military aircraft at one or more airfields in the former Soviet republic of Tajikistan, Afghanistan's northern neighbor. The U.S. military already is using one airfield in Uzbekistan.

Three Western reporters--two from France and one from Germany--were killed in northeast Afghanistan on Sunday when Taliban forces ambushed Northern Alliance fighters.

Meeting on new government

For now, diplomatic maneuvering has taken on new importance. UN officials said they expected a meeting to discuss forming a new Afghan government to take place in Europe, possibly in Geneva or Vienna.

Troops from Muslim countries such as Turkey, Bangladesh, Jordan and Indonesia could help the Afghan politicians reimpose order in Kabul if the Taliban collapses, but the UN would play mainly a supporting role, they added.

A declaration issued at the end of a 90-minute meeting endorsed efforts by the top UN envoy for Afghanistan "to facilitate efforts by Afghan groups committed to a free and peaceful Afghanistan to establish a broad-based Afghan administration on an urgent basis."