If Tibet were granted autonomy or independence, as thousands of protesters have demanded during the recent Olympic torch relays through Paris, London, and San Francisco, China’s Communist regime could face an existential threat, according to a range of experts on the region.

While many in the West think of Tibet simply as the picturesque area around Lhasa that lures tourists, Buddhists, and mountain climbers, the territory claimed by Tibetan activists is more than twice as extensive as the land Beijing designated in 1965 as the Tibet Autonomous Region. So-called Greater Tibet includes all of China’s largest province, Qinghai, as well as portions of three other Chinese provinces.

The government in exile of Tibet’s spiritual leader, the Dalai Lama, has laid claim to about 965,000 square miles in all, or roughly a quarter of China’s total land mass.

“How would I react if anybody was asking me to give up a quarter of my backyard or asking Mayor Bloomberg to give up one quarter of New York City?” a political science professor who specializes in China, Andrew Nathan of Columbia University, said. “It’s very much a hard-edged military issue to begin with. If you lose control over that territory, someone else gains influence there, whether it’s India, or America, or any of the powers that have traditionally had influence in Tibet.”

Mr. Nathan said Chinese leaders view it as a question of whether they should “occupy a territory where everybody hates your guts, or the alternative to that is, don’t occupy a vast area where everyone hates your guts?”

Another major concern for China is that concessions made to the Tibetans might quickly be demanded by others, such as the Muslim group known as Uighurs who make up the largest part of the population in another purportedly autonomous Chinese region, Xinjiang. “if they start negotiating with the Dalai Lama, everyone else is going to expect the same treatment,” Mr. nathan said.

Chinese fears that Tibet and Uighur activists are colluding against the center in Beijing are not without foundation. While the press made much of the presence of Richard Gere and Archbishop Desmond Tutu at a large public vigil for the Tibetan cause in San Francisco last week, Chinese officials likely took more interest in the speaking role given to a prominent Uighur dissident, Rebiya Kadeer.

Ms. Kadeer, who took up exile in America in 2005 after serving six years in a Chinese prison for leaking state secrets, led the crowd in a fiery chant. “Free Tibet now! Free Uighur East Turkestan now!” she cried, employing the phrase Uighur activists use to describe what China calls Xinjiang.

“We, the Uighur people, just the same as the Tibetans and the rest of the world, we demand our freedom,” she said, through a translator. “They must give us what belongs to us, our land and our freedom. … The Chinese government cannot eliminate us from the world, the Uighurs and the Tibetans.”

Removing both Tibet and Xinjiang from China’s control would excise nearly 43% of the nation’s territory, a scenario that it is hard to contemplate any Chinese leader accepting voluntarily.

On Saturday, President Hu of China made clear he views the Tibet issue as a threat to China’s national identity.

“Our conflict with the Dalai clique is not an ethnic problem, not a religious problem, nor a human rights problem. it is a problem either to safeguard national unification or to split the motherland,” Mr. Hu said, according to the state-run news agency, Xinhua.

A professor of Chinese history at Yale University, Jonathan Spence, said the fears of disintegration are deep-rooted and go beyond simply Tibet and Xinjiang. “China’s an accretion as a state,” he said. “There’s a feeling, i think, that some of these areas could easily get out of control.”

The Dalai Lama has said he does not favor independence from China, but he wants Tibet to be a weapon-free “zone of peace.” However, his stated demand for a democratically elected government could be an even bigger problem for Beijing.

“if it’s good enough for Tibetans to have their own constitution and free elections and religious freedom, then why not other parts of China?” Mr. nathan said.

A Tibetan writer who now lives in Mount Eagle, Tenn., Jamyang Norbu, said granting democracy to Tibet would eventually bring down the entire Chinese regime. “The rest of China is going to demand the same thing, which means the Communist Party has to go,” he said.

Mr. Norbu said many Tibetans reject the Dalai Lama’s approach because of the inherent implausibility that Chinese leaders would willingly set in motion a process likely to bring about their political demise.

“The Dalai Lama’s position is he’s hoping the Chinese government will negotiate away half of these provinces,” the Tibetan writer said. “I don’t think the Chinese are going to concede anything. They’re in a bind.”

Mr. Norbu said he’s “thrilled” about the Olympic-related protests, but is convinced that Tibet will be free only if some larger crisis befalls the Chinese government. “The hope is the Chinese empire will disintegrate,” he said.