ALONG THE AMU DARYA RIVER, Uzbekistan – The fall of a key
northern Afghan city to U.S.-backed rebels offered a military and
humanitarian breakthrough in America’s campaign against terrorism.

Northern Aliance rebels captured Mazar-e-Sharif, about 35
miles south of this river that forms the Afghanistan-Uzbekistan
border, after several days of attacks from the south supported by
American airstrikes.

Taliban officials said their forces withdrew. But it wasn’t
immediately clear how far, for how long, or whether Taliban forces
north of Mazar-e-Sharif (population 200,000) may still threaten
the supply route.

Mazar-e-Sharif is considered strategic because of its link
to Uzbekistan – a relatively good road south from the river, with
access to Kabul that is not as vulnerable to weather as the many
mountain passes in Afghanistan. The city also has an aiport that
the Northern Alliance reportedly controls.

Anti-Taliban troops who were massed at the front about 30
miles north of Kabul cheered at reports of Mazar-e-Sharif’s fall,
with villagers crowding around radios to hear the news.

“This is the beginning of the collapse of the Taliban,” said
Nur Agha, a 22-year-old fighter.

Alim Khan, a Northern Alliance commander, said anti-Taliban
forces would launch a major attack on the capital within three
days.

He said that 1,000 opposition troops would assemble today at
Bagram, site of an opposition-controlled air base near the front
line.

Mohammad Afzal Amon, the commander of the opposition’s elite
Zarbati troops north of Kabul, said 600 fighters had been sent to
his area since the victory in Mazar-e-Sharif.

But the opposition will likely face a much tougher battle for
Kabul, a city of about 1 million people, than it did at
Mazar-e-Sharif. Taliban forces are more numerous and the terrain
more mountainous. And the United States – whose warplanes would be
vital to any advance – has expressed reservations about the
alliance taking the capital.

Speaking at the United Nations, President Bush said he wants
the Northern Alliance forces to steer clear of Kabul, part of an
effort to assure that power is eventually shared among the various
tribes of the country.

“We will encourage our friends to head south but not into the
city of Kabul itself,” Bush said.

While Northern Alliance commanders relished their success at
Mazar-e-Sharif, signs of division are emerging in the group’s
political leadership.

Alliance officials say two factions have emerged in the two
months since the assassination of the alliance’s leader, Ahmed
Shah Massood: the younger, pro-Western, religious moderates and
the older, religious conservatives, who are more skeptical of the
West.

A senior alliance official said the power struggle had
emerged because officials and commanders feared they would lose
the power, wealth and status they enjoyed if a new government was
formed.

The more conservative wing includes the alliance’s president,
Burhanuddin Rabbani, and one of its more senior Pashtun leaders,
Abdul Rasul Sayyaf, the official said.

The more moderate wing, he said, includes the foreign
minister, Dr. Abdullah Adbullah; the interior minister, Yunos
Qanooni; and Anwari, leader of ethnic Hazara forces fighting in
the alliance, who has only one name.

The capture of Mazar-e-Sharif and the planned Kabul offensive
increase urgency for forming a post-Taliban government. But so
far, government-building has moved slowly, in part because of the
struggle within the alliance.

The prospect of humanitarian aid getting through may be the
most immediate impact of the fall of Mazar-e-Sharif.

United Nations officials in countries around Afghanistan
warned again of a humanitarian crisis with more than 100,000
children and women in Afghanistan dying if more humanitarian aid
doesn’t move soon. The Taliban has seized aid and made it
difficult to deliver, aid workers say.

Along this river at the port town Termiz, U.N. relief
agencies have amassed more than 1,000 tons of food. Crates of
biscuits and milk for babies sit in storage, as do rudimentary
health kits. A long runway at Termiz allows direct delivery of aid
from abroad.

But security concerns about terrain immediately across the
Amu Darya – sand dunes and scrub land recently controlled by
Taliban forces and possibly mined – blocked aid efforts Saturday.

Government officials from Uzbekistan said they planned to
visit the border today to assess the situation.

The U.N. also is taking stock, said Rupa Joshi, a UNICEF
regional spokeswoman.

“Our mission is to get as much aid across as possible as soon
as possible,” Joshi said.

A senior U.S. aid official is scheduled to arrive today in
the Uzbekistan capital, Tashkent.

U.S. officials said Andrew Natsios, administrator of the U.S.
Agency for International Development, will meet with U.N. and
other aid agency officials at Termiz this week. The visit is part
of a multicountry swing planned before the latest military action.

The Friendship Bridge at Termiz spans the mile-wide, muddy
river.

Uzbek tribal leader Rashid Dostum first captured
Mazar-e-Sharif, where ethnic Uzbeks live, in the mid-1990s after a
siege. Taliban forces recaptured the city in 1998 after another
deadly battle. Each side committed atrocities, according to a UN
investigation.

Uzbeks agreed last month to let barges loaded with
humanitarian aid cross the river at Termiz to Afghanistan. From
there, Afghan employees of international aid groups could move
supplies to Mazar-e-Sharif and points along the way, UNICEF
spokeswoman Joshi said.

Rather than military maneuvers, aid officials focused on
moving a first barge on Wednesday if possible, said Mohammaed
Kumbakumba, UNICEF’s logistics chief at Termiz. It doesn’t matter
who controls what, he said, as long as the supplies reach the
children.

The New York Times and The Associated Press contributed to this
report.