WASHINGTON, Oct 22 (AFP) - Exiled Tibetans opposed to China's rule over their Himalayan homeland plan to step up a campaign on behalf of a Tibetan scholar whom China has now acknowledged detaining.

The International Campaign for Tibet (ICT) is "trying to see if members of Congress will take up this case and ask (China) for evidence," said ICT official Bhuchung Tsering.

"We're also trying to see what action the United Nations can take" on behalf of Ngawang Choephel, a Tibetan music scholar who disappeared in Tibet in September 1995, he said.

In a letter to a US congressman dated October 15 and circulated Tuesday,

Shao Wenguang, a counsellor at the Chinese embassy in Washington, said Chinese authorities believe Choephel was sent on a US-funded spying mission in Tibet.

"We have learned that, funded by some Americans, Ngawang Choephel was sent by the Dalai Lama's 'government-in-exile' to Tibet, where he used the cover of collecting Tibetan folk songs to gather sensitive intelligence and engaged in illegal separatist activities," Shao said.

The letter failed to say where Choephel was being held or whether he had been formally charged with any offense.

Choephel, who was studying in the United States on a Fulbright scholarship, is suspected of violating a broad security law against acts aimed at overthrowing the socialist system or stealing state secrets for an enemy, Shao's letter said.

Human rights groups and several dozen members of Congress have pressed the Chinese government for more information about Choepel, who is believed to have been transferred to a prison in the Tibetan capital, Lhasa.

The Tibetan government-in-exile, based in the Indian town of Dharamsala, strongly denied earlier Tuesday that it had sent Choephel on a spying mission.

Tsering, who knew Choepel in Dharamsala, said the young man would be an unlikely spy in any event, describing him as introverted and scholarly.

"He wasn't very outgoing," Tsering said. "He was more interested in his own performing arts tradition than in politics ... He's a scholar and a musician, not an activist."

Choephel, a member of the Dharamsala-based Tibetan Institute of Performing Arts, was granted a Fulbright scholarship in 1993 to study and teach ethno-musicology at Middlebury college in the northeastern US state of Vermont.

Tempa Tsering, secretary of the exiled government's department of Information and International Relations and no relation to Bhuchung Tsering, said his primary concern was Choephel's well-being.

"Right now, our main concern is the safety and health of Ngawang Choephel," Tempa Tsering said, adding that his only crime was "trying to preserve the rich Tibetan musical heritage which the Chinese have (suppressed) to suit their claim over Tibet."