Among the pilgrims at the gates of the Jokhang temple, the holiest Buddhist site in the capital of Tibet, a Chinese migrant and avowed atheist named Xie Danchun was doing a brisk business. He sells white Tibetan prayer scarves, known as hada, symbols of a culture struggling under periodic assault from authorities in Beijing.

"It's a job," mused Xie, a 24-year-old from Sichuan province, as pilgrims prostrated themselves in the swirling incense smoke outside the 1,300-year-old shrine. "Besides, the silk factory is in my county back home. We run it up here on my county's trucks."

On any given day, an estimated 100 million people are on the move across China looking for work. But perhaps nowhere is China's vast internal migration having a more profound effect on the local population than in Tibet. The arrival here of tens of thousands of job seekers from China's ethnic Han majority, while a minor runoff in a country of 1.3 billion people, is threatening to swamp the culture of 5 million Tibetans.

"I'm not replacing a Tibetan," argued Xie, who came here in pursuit of a fortune two years ago after China relaxed restrictions on travel. Pointing to a teenage Tibetan competitor who was selling scarves of lower quality at the same price, he said, "We're just beating them at their own game."

The fate of Tibetan culture has taken on a new urgency in recent months since the World Bank approved a $160 million loan, over U.S. and German objections, that included millions to help move 58,000 people, including some Han Chinese, onto land claimed as traditionally Tibetan.

Opponents charge that the resettlement, designed to give farmers from an overpopulated region access to more land and water, will speed the assimilation of Tibetans, a deeply religious people whose language, world view and customs differ sharply from the Chinese. Controversy around the project grew in August when Chinese authorities detained American activist Daja Meston, an Australian, and a Tibetan interpreter after they traveled near the project's proposed site in Dulan county. While in police custody, Meston jumped from a window and broke his back. He was later released and after treatment at a Boston hospital is now recovering at his home in Massachusetts.

Proponents of the resettlement plan point out that Dulan county, the site of the project in Qinghai province just north of Tibet, is already largely Han Chinese, and that some Tibetans will be included in the resettlement of the 58,000 people. They argue that the area is not in Tibet proper but in a region that has long included an ethnic mosaic of Tibetans, Mongols, Muslims, Turkic peoples and Han Chinese.

But critics see in the plan a pattern in which China is encouraging Han Chinese to move into restive regions once populated purely by minority peoples.

"The feeling we have is that the Chinese government is encouraging population settlement even more in the traditionally Tibetan regions than before," said John Ackerly, a director of the International Campaign for Tibet in Washington. "This is not good news for Tibetan culture."

China's Communist government and its imperial predecessors have long subdued troubled regions through migration. In the 1950s, hundreds of thousands of Han Chinese soldiers and officials were dispatched to the mostly Muslim northwest territory of Xinjiang. Today, an estimated 5 million Han Chinese live in the region and Urumqi, its capital, has become overwhelmingly a Chinese city. In Inner Mongolia, once home to more Mongols than Han, the Han now dominate by a ratio of about 5 to 1.

Tibet, too, has received its share of planned migration. Since 1959, when a Tibetan rebellion against China's rule was repressed by the military, more than 111,000 Chinese officials have been sent to the region as agents of "modernization," according to Nima Tsering, a vice governor of Tibet.

"This is a social system that was dark and backward, a little like the Middle Ages in Europe 500 years ago," Tsering, a Tibetan who has allied himself with the Chinese Communists, told a group of Western reporters recently. "In the 1950s, while you were making satellites and modern industry, we didn't even have roads."

He questioned why he should want to restrict Chinese from settling in Tibet. "I want them to come," he said.

While some critics of China's government have explained such policies as part of a deep-seated Chinese sense of manifest destiny, resettlement is also seen by Chinese authorities as an issue of national security.

Although 93 percent of the Chinese population is Han Chinese, ethnic minorities inhabit regions that contain a vast percentage of China's material wealth. Minorities predominate in 60 percent of China's territory, including regions crucial to China's supply of natural resources such as timber, water and petroleum. Areas dominated by China's two most recalcitrant minorities--Tibetans and Muslim Uighurs--comprise 1.5 million square miles, almost half of China and much of its historically vulnerable border areas.

Chinese strategists argue that the government naturally wants to fill such areas with Han Chinese presumably loyal to Beijing. One senior Chinese analyst compared China's move to resettle Han Chinese in Tibet and Xinjiang to population changes in Alaska. In the 1940s, he noted, native Alaskans made up more than half the population in what would become the state with the largest area. Today, they constitute about 15 percent. "So are we both guilty of cultural genocide?" he asked.

Chinese migration to Tibet has been uneven over the last four decades. In the 1960s and 1970s, after the Tibetan rebellion, China dispatched officials to govern Tibet but banned ordinary Chinese from moving there. In 1980, China acknowledged committing grave mistakes in Tibet, such as destroying almost every Tibetan Buddhist monastery during the Cultural Revolution of 1966-76, and instituted a program to limit the number of Chinese officials shipped into Tibet.

But in 1984, China also began dispatching huge work teams into the province to build roads and other infrastructure. In the early 1990s, authorities dismantled checkpoints leading into the region so Chinese looking for work could move there. While cities such as Beijing and Shanghai took steps to limit the traffic of the mass of unemployed from China's countryside, Tibet encouraged them to come.

One recent newcomer is Li Tiegang. Last year the 25-year-old was demobilized from the military as part of a program to trim 500,000 men from the People's Liberation Army. Li, who had been posted to Tibet, decided to stay with 120 other men from his county, all former soldiers.

The army arranged a loan for him, he bought a car and now he's a taxi driver on the same streets he patrolled as a soldier. The $400 a month he earns is equivalent to what his parents made in one year back in his hometown in rural Anhui province. "I'm sending money to them for the first time," he said. "I'm working 16 hours a day but I'm finally saving something."

Signs of Chinese life predominate in Lhasa, the Tibetan capital. Since 1950, the actual size of the city has expanded 17 times, with the Chinese sections of town growing the most, bringing some amenities and boxy Chinese architecture. When Xu Yongping, the deputy chief of Tibet's Office of Post and Telegram, was sent to Lhasa after graduating from a university in Beijing in the early 1980s, he said the city had only three barbershops and no vegetable markets.

"We used to grow cabbage in the dirt outside our apartments," said the Han Chinese executive. "Today, it's a lot better."

Chinese traders control most of the food markets in the city. Peaches, for instance, are brought in by Chinese from several counties in Sichuan. It's a complete monopoly. Old Han Chinese women from the neighboring province hawk the fuzzy fruit from wooden carts on Lhasa's back streets.

"We are poor back home," said one wizened street seller, Han Fanchao. "In Lhasa, we are much better. I just wish Tibet's altitude wasn't so high. . . . It's hard to breathe."

Chinese karaoke halls, noodle stalls and brothels line the streets of Tibet's cities. Even the prostitutes are mainly Han. The proprietor of one glitzy night club, the Peach Blossom Dream, said the prostitutes come from all over China because Han workers enjoy spending an evening with someone from their hometown.

"They speak the local dialect," he said. "They feel closer that way."

There are no official figures for the number of migrant Chinese in Tibet's cities but the numbers are booming. Chinese officials say Lhasa's population remains close to 90 percent Tibetan and that in total more than 95 percent of Tibet is Tibetan. But Li, the former soldier, and tens of thousands like him are not counted by Chinese census takers.

Li competes with Tibetan cabbies for fares. His brother, Tieshu, is in construction and is vying with Tibetan laborers for jobs laying bricks. Like many Chinese, they both look down on the Tibetans. "They're low quality people," Tiegang said. "So it's easier for me to make money here."

But Li and his brother said they had no plans to live permanently in Tibet. Most Chinese leave Tibet after two or three years and many move home for the winter.

"There is something a bit tenuous about the Chinese presence in Tibet," said Ackerly, who has traveled the region extensively. "Once you get above 9,000 to 10,000 feet and outside the cities, there are just no Chinese. That's the one hopeful sign. Most Chinese really don't want to be there."

Ackerly predicts that if a significant political loosening occurs in China, many Han Chinese would leave Tibet. "You won't have the problem you have now in the Baltic states with the Russian presence being an enduring problem due to the higher standard of living," he said. "Tibet is too poor. The Han would all go home."

CAPTION: Xie Danchun, who moved to Tibet from Sichuan province, sells prayer scarves near a temple in the capital. Han Chinese are drawn there by business opportunities, lucrative government incentives.

CAPTION: The Li sisters moved to Tibet three years ago and now run an electrical goods store in Lhasa.