Fellow activists say Chen Guangcheng, a blind lawyer who exposed forced abortions and sterilizations as part of China's one-child policy, fled house arrest a week ago and has sought protection at the U.S. Embassy in Beijing.
Neither the U.S. nor Chinese government has confirmed the reports, but the saga looks set to overshadow this coming week's Strategic and Economic Dialogue in the Chinese capital. Secretary of State Hillary Rodham Clinton and Treasury Secretary Timothy Geithner are leading the U.S. side at the talks beginning Thursday.
A potential further complication is a letter from the White House director of legislative affairs, Rob Nabors, to Sen. John Cornyn, R-Texas, explaining that the Obama administration would consider selling new U.S. warplanes to Taiwan. A sale would infuriate China, which considers the island nation an integral part of its state even after their split more than six decades ago.
Chen's status and the fighter jets represent the latest strains in Washington and Beijing's up-and-down relationship in recent years. President Barack Obama has sought to "pivot" American military might and diplomatic energy toward Asia to improve America's standing in the region and check the expansion of Chinese power, and achieved mixed results.
The two issues underscore the fundamental disconnect between the world's No. 1 and No. 2 economies, the top importer and exporter, and the biggest military and the fastest developing, on issues from human rights and Taiwan to currency policy and combating nuclear-armed North Korea and potentially nuclear-armed Iran.
A Texas-based activist group that has been active in promoting Chen's case said China and the U.S. were discussing the fate of the 40-year-old.
"Chen is under U.S. protection and high-level talks are currently under way between U.S. and Chinese officials regarding Chen's status," said a statement from the ChinaAid Association. It cited a source close to the situation.
The U.S. Embassy in Beijing declined comment. Chinese Vice Foreign Minister Cui Tiankai said he had no information on Chen's case.
The case is so sensitive that officials in Washington have been ordered not to say anything about it at all. That was underscored on Friday and Saturday by the absolute refusal of the White House to speak out on the matter and the State Department pretending that nothing unusual was afoot.
After making several public appeals this year for Chen's release, State Department spokeswoman Victoria Nuland would say only that "we have spoken out about his case in the past."
"We have always had concerns about this case," she said Friday, adding: "I don't have anything current on this issue today."
The top U.S. diplomat for Asia, Assistant Secretary of State Kurt Campbell, originally was due in Beijing in the coming week, but he arrived early Sunday in the capital and did not speak to reporters. Earlier, department officials in Washington had ignored or declined to respond to questions about indications that Campbell had been dispatched earlier than planned ahead of the talks to smooth things over with the Chinese.
ChinaAid's founder, Bob Fu, said Chen's case was a benchmark for the United States and its human rights image around the world.
In February, a former regional chief of police, Wang Lijun, visited a U.S. consulate to raise concerns about the murder of a British businessman and possible links to powerful Chinese politician Bo Xilai. Wang expressed interest in seeking asylum with the U.S., but was turned away, raising eyebrows among Republican lawmakers in the United States.
Chen's case has become an embarrassment for Beijing. Fu and Chinese-based activists say he slipped away from his intensely guarded home on the night of April 22. His wife and 6-year-old daughter are still there.
Chen recorded a video as a direct address to Premier Wen Jiabao, condemning the treatment of him and his family and accusing local Communist Party officials by name. Activists sent the video Friday to the overseas Chinese news site Boxun.com, which posted part of it on YouTube.
If Chen is in the U.S. Embassy or with U.S. officials at another location, it is not known how he would be able to leave or where he could go without Chinese permission. There was no extra security outside the U.S. Embassy in Beijing on Saturday.
In 1989, Fang Lizhi, whose speeches inspired student protesters throughout the 1980s, fled with his wife to the U.S. Embassy after China's military crackdown on the pro-democracy movement. He was forced to stay there for 13 months before China eventually let the couple leave the country. Once China's leading astrophysicist, he died April 7 at age 76 in Tucson, Ariz., where in exile he was a physics professor at the University of Arizona.
Chen is widely admired by rights activists in China who last year publicized his case among ordinary Chinese and encouraged them to go to Dongshigu village and break the security cordon. Even Hollywood actor Christian Bale tried to visit, but was roughed up by locals paid to keep outsiders away
A self-taught lawyer blinded by fever in infancy, Chen served four years in prison for exposing forced abortions and sterilizations in his and surrounding villages. Since his release in September 2010, local officials confined him to his home. Amnesty International and other human rights groups say he was abused over the last 18 months.
But Washington will have to weigh its response at a time it is seeking China's help on many issues around the world, from trying to restrain North Korean and Iranian nuclear ambitions to forcing Syria's government into observing a cease-fire. There are also debates about currency and trade policy considered highly relevant to U.S. and global economic recovery.
Alongside Russia, China has brushed aside American pressure to raise the pressure on Syria despite repeated U.S. warnings that those in opposition will end up on the wrong side of history. China has shielded North Korea from tougher international action despite the reclusive communist government's continued nuclear activity and a series of provocations that nearly plunged the Korean peninsula into war two years ago.
The overtures have left Obama vulnerable to charges that he is being naive or too accommodating to China. Republican critics, including likely presidential nominee Mitt Romney, say the administration hasn't pressured China enough on issues vital to U.S. economic and strategic interests.
Since Obama took office, China's booming economy has driven global growth while the U.S. has struggled to emerge from its worst economic downturn since the Great Depression.
Greater Chinese assertiveness has resulted in clashes with the U.S. over naval vessels in the Yellow Sea and American exporters trading with Taiwan; with Japan over fishing rights; and with Southeast Asian nations over claims to the resource-rich South China Sea.
But Washington has pushed back. To ease concerns posed by the threat of China-backed North Korea, the U.S. has strengthened military alliances with South Korea and Japan. By speaking out against China's maritime claims, it has improved ties with Southeast Asian nations fearful of an expansive and potentially belligerent Beijing.
U.S. relations with Vietnam and the Philippines in particular have benefited. Even reclusive Myanmar, long an international pariah protected by China's diplomatic sway, has initiated democratic and human rights reforms to improve its standing with the U.S. and the West. The U.S. also has led talks on a new regional trade pact that would exclude China.
With the Iraq war over and combat operations in Afghanistan ending over the next couple of years, Obama has recalibrated U.S. focus on Asia and its booming markets such as China, India and Indonesia. More than half of the world's population lives in Asia, which is seen as the future center of the world economy.
Previous rounds of the U.S.-China dialogue have been hailed as productive and have included new educational and scientific exchanges. But they haven't resolved points of contention over Taiwan, Tibet and human rights.
U.S. arms sales to Taiwan particularly rankle China, and the irritation could grow worse with the emergence of the White House letter.
China has 2,300 operational combat aircraft, against only 490 for Taiwan. In September, the U.S. turned down a Taiwanese request for 66 relatively advanced F-16 jet fighters, while agreeing to help Taiwan upgrade its existing F-16 fleet. Critics accused the White House of yielding to pressure from China.
China and Taiwan split amid civil war in 1949. Despite improving relations over the past four years, China still threatens to attack across the 100-mile-wide Taiwan Strait if the democratic island seeks to declare independence.