WASHINGTON — US lawmakers vowed support for Tibet and exiles prayed outside of the White House, launching worldwide rallies 50 years to the day Tuesday of an uprising that forced the Dalai Lama to flee.

As China poured troops into the Himalayan region, Tibetans overseas called demonstrations from Washington to the small Indian town of Dharamshala where the Dalai Lama -- now 73 and boasting a global following -- lives in exile.

A US lawmaker on Monday introduced a resolution to Congress that would urge China to end its "repression" of the Himalayan region.

House Speaker Nancy Pelosi, a longtime supporter of Tibet, vowed that Congress would "overwhelmingly" approve the bill on the anniversary on Tuesday.

"The situation in Tibet challenges the conscience of the world," Pelosi told Tibetans and their supporters inside the US Capitol.

"If freedom-loving people do not speak out for human rights in China and Tibet, then we lose the moral authority to talk about it in any other place in the world," she said to loud applause.

China on Tuesday called for the measure to be withdrawn.

"We express serious concern over this ... we believe the US Congress resolution proposed by a few anti-China representatives disregards the history and reality of Tibet," foreign ministry spokesman Ma Zhaoxu told reporters in Beijing.

"We request relevant US representatives to ... stop pushing the Tibet bill," the official said.

US actor and activist Richard Gere lobbied members of Congress to speak out about Tibet. China's Foreign Minister Yang Jiechi is visiting Washington this week amid tension over a naval incident between the countries.

Gere said he hoped Secretary of State Hillary Clinton misspoke last month when she said that human rights would take a back seat to Washington and Beijing working together on fighting the economic crisis and other issues.

"For the good of America -- for Americans as well as the rest of the world -- you have to say what you stand for," Gere told AFP. "And words have to be spoken over and over again in every situation."

At noon (1600 GMT) in Washington -- midnight in Lhasa -- hundreds of exiles holding Tibetan and US flags bowed their heads in prayer in Lafayette Park facing the White House.

"We are here to tell the world that 50 years of occupation, 50 years of persecution, 50 years of genocide is too long," said Tsering Palden, president of the Tibetan Youth Congress activist group's New York chapter.

"This struggle for Tibetan freedom will gain momentum until Tibet is free," he said to chants of "Free Tibet!".

The protesters marched to the Chinese embassy joined by one of China's most famous dissidents, Wei Jingsheng, who has questioned historical claims to Tibet put forward by his country's leaders.

"The Tibetans have been deprived of their right to protest but we can see that they are very strong," Wei told AFP.

The Dalai Lama sneaked out of Lhasa on horseback on March 17, 1959 after the Chinese launched a crackdown. Tibet's government-in-exile says that more than 87,000 people died between March and October of 1959 alone.

Tibet's exiled government says at least 200 more people died when Chinese security forces clamped down following last year's protests that marked the 49th anniversary.

The International Campaign for Tibet issued a report Monday listing names and details of 600 Tibetans it said were still unaccounted for -- and estimated the real figure was more like 1,200.

The protesters outside the White House included Ngawang Sandrol, who was a young nun when she was arrested in 1992 for chanting "Long live the Dalai Lama."

She said that prison guards beat her and came to her with "a strange object that looks like a telephone.

"They asked me, 'Do you want to call your home?' And I said my home doesn't have a telephone," she told the rally in a hushed voice.

"Then he put the strange object into my shirt and turned it on. My entire body shook in a way I couldn't control. That was my first time with electric shock and I was 13 years old."

Under international pressure, China in 2002 freed Ngawang and later allowed her to move to the United States.

"I know from my own experience that it is helpful when free people in free nations put pressure on the Chinese government," she said.