UETTA, Pakistan, Sept. 29 ・Refugees arriving here after arduous journeys from Afghanistan are describing scenes of desperation and fear at home as the threat of American-led military attacks turns their long-running misery into a potential catastrophe.

Cities and towns are emptying as people defy orders from the governing Taliban and try to flee. Those with enough money are paying smugglers to take them to Pakistan. Others are marooned at closed border gates or hiding in the Afghan countryside.

United Nations relief officials warned that the precarious situation in Afghanistan and deprivations from a three-year drought threatened to snowball into a major disaster. Officials estimate that 1.5 million Afghans will try to leave the country and that two million to three million more could face starvation inside.

"The worst-case scenario is when nobody can get out and aid cannot get in, because we know the crisis is already serious," Rupert Colville, a spokesman for the United Nations refugee agency here, said in an interview.

The scope of the crisis will depend on many factors, including the extent of military action against Afghanistan. But United Nations officials stressed that they were preparing for the worst as they hoped for less severe problems.

Even before the threat of American retaliation, Afghanistan faced severe food shortages. From three million to four million people rely on aid from the World Food Program, and stocks are within two weeks of running out in some areas, officials said.

The threat of military strikes forced the removal of international aid workers, crippling assistance programs. The Taliban have restricted communications between outside agencies and Afghan staff members still in the country, the United Nations and other organizations said.

The five countries that border Afghanistan have closed their borders, fearing an influx of terrorists concealed among the refugees and new burdens on their own economies. Tens of thousands are waiting at crossing points on the borders with Pakistan and Iran, aid workers said.

The United Nations secretary general, Kofi Annan, is seeking donations of $584 million to try to limit the misery and to prepare for the expected exodus. Mr. Colville said that $30 million in aid was needed for immediate preparations and that $12 million had been pledged, with $4 million from the United States. Angelina Jolie, the actress, a good- will ambassador for the United Nations relief agency, donated $1 million.

The first aircraft carrying United Nations supplies arrived in Quetta this afternoon. At about the same time, a convoy of trucks from Unicef left the Pakistani border town of Peshawar carrying 20 tons of wheat and other supplies to refugees inside an area of Afghanistan held by military forces opposed to the Taliban.

Those who have managed to escape to this provincial capital in southwestern Pakistan in recent days described harrowing journeys over difficult terrain. They were in constant fear of bandits and bribe seekers. Villages along the way had little drinkable water, and meager supplies of food were often kept under armed guard.

Aid workers said they had no accurate count of how many people had arrived here. Pakistani officials sent back 15,000 refugees this month. The new refugees, afraid of the same fate, vanish into the network of camps inhabited by 100,000 or more of their countrymen who have arrived in waves since the Soviet invasion in 1979.

Homayoun Barak, director of a nonprofit medical service, the Guardians, which runs clinics here and in Kandahar, Afghanistan, said new refugees had health problems that included severe diarrhea, malnutrition and tuberculosis.

Television is banned in Afghanistan. Word of the attacks on America and the potential reprisal was broadcast on the Voice of America and the BBC World Service. Mr. Barak said that when he left Kandahar a few days ago, stores had sold virtually every radio set to nervous residents.

Rahim Ullah stayed in Afghanistan through the Soviet invasion and the civil war that followed. He said he was too frightened of the prospect of American bombs to keep his family in their town outside Kandahar.

"We don't fear the Taliban," Mr. Ullah said as he stood on the barren, parched ground surrounding the Tokhi-Abad refugee camp, on the outskirts of Quetta. "We came here because war is coming."

Mr. Ullah, 36, paid a smuggler $30 to transport his family across the border. He and his wife huddled with their five young children for three days in a wagon as a tractor pulled them laboriously through the low mountain passes and across the border at a remote point southwest of Quetta, a 150-mile trip.

Their home now is a four-room mud-brick house given to them by a relative. The little food they are able to buy is cooked on a stove fueled with scraps of waste paper and garbage scrounged by the oldest children. The youngest, a 1-month-old girl named Anar Bibi, is pale and sick from hunger.

The rugged terrain along the border in this remote region is laced with hundreds of hidden trails used by drug traffickers and black market smugglers. Muhammad Noor and 14 family members rode a truck along one of those routes to go to Pakistan from Kandahar.

"America will be coming to attack, and it will make things worse for us," Mr. Noor said as he squatted in the small house where he and his family have moved in with his brother. "We came here because of the coming war."

Two women who left Kandahar by taxicab were turned back at the Chaman crossing point, Mr. Colville of the United Nations said. The cab was allowed to cross, and the women found their way over the border on foot and met the driver at an arranged site.

Several refugees said they had been waylaid by Taliban militia members who took away the young men in their parties at gunpoint, demanding that they stay and fight the American invaders.

"My 21-year-old son was taken," said Zaman Shah, who joined relatives crammed into a small mud- brick house at Tokhi-Abad after fleeing Afghanistan with the rest of his family last week. "I could do nothing to stop them."