The blind legal activist Chen Guangcheng left the refuge of the U.S. Embassy in Beijing for a hospital on Wednesday, but he was quickly cordoned off by Chinese police and reportedly seized by misgivings about his decision, as an apparent diplomatic triumph risked dissolving into a damaging episode in U.S.-China relations.

After four days of secret negotiations, U.S. diplomats on Wednesday initially touted then later scrambled to defend their role in forging an agreement that they said contained extraordinary Chinese promises to allow Chen — a self-taught lawyer known for criticizing Chinese policies on abortion — to move his family to Beijing, where he would begin a new life as a university student.

Chinese officials, by contrast, broke their official silence on Chen by firing a broadside complaining about U.S. interference in China’s internal affairs. The Foreign Ministry demanded an apology, which State Department officials declined to give.

The confusing, chaotic episode coincided with a visit to China by Secretary of State Hillary Rodham Clinton and Treasury Secretary Timothy F. Geithner, who arrived in Beijing on Wednesday with an entourage of diplomatic and trade officials intent on smoothing relations and increasing economic and cultural ties.

The Obama administration wants greater cooperation from China on trade, currency rates, Iran oil sanctions and North Korean nuclear weapons, but with the Chen case, the issue of human rights threatens to overtake that agenda.

Chen’s case also quickly entered the presidential campaign. “I really love America,” Mitt Romney, the presumptive Republican nominee, said at a Virginia fundraiser Wednesday night. “I love what it represents, and I love that a Chinese dissident who fled the policies in his country, I love where he went — to our embassy.”

Chen revived the human rights issue by escaping from de facto house arrest in his home village in Shandong province on April 22 and by seeking U.S. protection in the Chinese capital four days later. American officials said Wednesday that they accepted him at the embassy on humanitarian grounds.

A familiar name

Chen was already well-known to U.S. officials. According to WikiLeaks, between April 2007 and July 24, 2009, his name was included in at least 37 State Department cables. His was one of three “key cases” mentioned during the May 2008 resumption of the U.S.-China human rights dialogue after a six-year hiatus.

So U.S. officials were elated when the Chinese government said it would allow Chen and his family to move away from their village and pledged to investigate why authorities there allowed armed thugs in plainclothes to confine the activist and prevent others from seeing him.

But Teng Biao, Chen’s lawyer, said in an interview late Wednesday that he had spoken with Chen several times during the evening. “He felt his safety is threatened. He feels pressure now,” Teng said. “In fact, from his language, I can tell that the decision to leave the embassy was not 100 percent his idea.”

“I spent most of the time trying to persuade him to go to the U.S.A.,” Teng said. “We discussed what to do next, staying in China or going to the States. After some discussion with friends, I feel his safety cannot be guaranteed if he stays in China.”

Teng said on Twitter Thursday that Chen did not have all the information available to him when he was inside the embassy. He said Chen’s wife, who had been isolated for years in their Shandong village farmhouse, also did not earlier have enough information to make appropriate decisions about their future, while they were negotiating for Chen to leave the embassy. Teng said he could no longer speak to the media.

Some China experts said they saw the pledges from Beijing not only as a human rights achievement but as an indication that — as in the recent case of Chongqing party leader Bo Xilai or last year’s ouster of corrupt local leaders in a strife-torn southern town — the central government wants to assert its authority over renegade or corrupt provincial authorities.

In addition, the agreement appeared to take Chen off the bilateral agenda. American officials released a photograph showing a smiling Chen with U.S. Ambassador Gary Locke and insisted that the activist left the embassy of his own volition.

Looking to leave China?

But friends of Chen criticized U.S. officials for leaving him unaccompanied at the hospital, where he was treated for a foot injury. Adding to the confusion, Chen told several reporters by phone from his hospital bed that he now wanted to move to the United States with his family.

Under intense international scrutiny, U.S. diplomats scrambled to provide their version of events.

“I was there,” Kurt Campbell, the State Department’s top diplomat for East Asia, said in a statement. “Chen made the decision to leave the Embassy after he knew his family was safe and at the hospital waiting for him, and after twice being asked by Ambassador Locke if he was ready to go. He said, ‘Zou’ — let’s go. We were all there as witnesses to his decision, and he hugged and thanked us all.”

Locke said the U.S. Embassy was prepared to house Chen for years, if that was what he wished, but that Chen insisted on leaving the embassy to be reunited with his wife. He spoke on the phone twice with his wife on Wednesday, said Locke, and she implored him to leave and join his family at the hospital.

Speaking at a press conference Thursday, Locke emphasized that the goal of U.S. officials was to determine what Chen wanted and then help him get it by acting as go-between negotiators with the Chinese government.

“He made it very, very clear form the very, very beginning that he wanted to stay in China, that he wanted to be part of the struggle, to improve the human rights within China and to gain greater liberty and democracy for the people of China,” Locke said. “We asked him, ‘Do you want to go to the United States?’ He said no.”

Locke said Chen wanted his wife to be brought to the hospital, where he would talk with her on phone and decide whether to leave the embassy or stay.

Chen spoke with his wife twice on Wednesday after she arrived at the hospital, said Locke. Chen’s wife spoke in the presence of a U.S. Embassy employee and away from Chinese government officials.

“She was imploring him to come to the hospital to be reunited with the family,” Locke said. Chen then decided to leave.

“I can tell you unequivocally that he was never pressured to leave. He was excited and eager about leaving when he made this decision,” Locke said.

A senior State department official said U.S. officials were spending Thursay trying to establish what Chen in fact wants to do before exploring any further ways to help him.

“Our understanding now from the contacts that we have had with his wife is that his view of what the best thing for him and his family may be changing,” the official said. “But we do not yet have a full view of what he wants to do at this stage so we are spending today endeavoring to clarify whether his position has chnaged and what he now wants.”

Soon after Locke and State Department legal adviser Harold Koh dropped Chen off at the hospital on Wednesday, the diplomatic frictions grew.

A combative statement from the Chinese Foreign Ministry heightened fears among Chen’s supporters that the deal could be unraveling. Fuming over the United States’ acknowledgment that it had sheltered Chen, Foreign Ministry spokesman Liu Weimin said, “The U.S. method was interference in Chinese domestic affairs, and this is totally unacceptable to China.”

According to the state-run news agency Xinhua, Liu added: “China demands that the United States apologize over this, thoroughly investigate this incident, punish those who are responsible and give assurances that such incidents will not happen again.”

Campbell said that the United States would not apologize but that Washington did not expect a similar incident to occur, a formulation U.S. officials hoped would be sufficient to mollify Chinese officials.

Meanwhile, Zeng Jinyan, the activist whose Twitter messages provided the most detailed information about Chen once he reached the hospital, put out another message Thursday saying she was now under house arrest in Beijing.

Zeng’s Twitter message said police agents in a black car followed her Thursday morning as she drove her daughter to kindergarten. She said the police then followed her back home and said she was officially under house arrest.

Zeng later answered the telephone briefly at her home after noon Thursday and said quietly, “Right now my situation is not good. My situation is complicated ... I cannot accept interviews.” Since then, her communications have been apparently cut off.

Zeng’s husband, AIDS activist Hu Jia, is away from Beijing at a conference in another part of China, and said he had been unable to contact his wife.

As the high-level diplomatic and trade talks began Thursday morning, there was no public mention of Chen, but there were allusions to the case.

Opening the sessions, Councilor Dai Bingguo asserted China’s right to determine how best to run its society.

“I wish to point out in particular that a fundamental way to manage state-to-state relations is . . . to respect each other’s sovereignty . . . and choice of social system,” Dai said. “No one should expect the Chinese to leave their own path.”

Clinton broached the topic of human rights toward the end of her remarks after listing other issues on the agenda, including North Korea’s nuclear program.

“The United States raises the importance of human rights and fundamental freedoms because we believe that all governments have to answer to their citizens’ aspirations for dignity and the rule of law,” she said, “and that no nation can or should deny those rights.”

A diplomatic dilemma

Chen’s case had presented the United States with a thorny diplomatic dilemma. He wanted to remain in China to fight for citizens’ rights, friends said. But with security officials rounding up the activists who helped him escape and who sheltered him, U.S. diplomats risked seeing Chen arrested if he left the embassy without some formal guarantees for his safety.

U.S. officials said the Chinese agreed to investigate the “extralegal” activities of local authorities in Chen’s home town who have allowed armed men to effectively confine the activist to his farmhouse for 19 months, preventing celebrities, journalists and others from visiting him.

Senior U.S. officials said they became extremely close with Chen during the negotiations, often holding his hand as they spoke. One official described the talks with Chinese officials as “intense but collaborative.”

The officials said American diplomats “will take a continuing interest in the case of Mr. Chen and his family” and will check on him in “regular intervals” to confirm that the Chinese government’s commitments are carried out.

But activists’ fears over Chen’s fate mounted, and they expressed increasing alarm — fueled by a series of Twitter updates — that what seemed like a human rights victory was spiraling quickly into a worst-case scenario.

Chen was no longer under U.S. protection, they noted. While U.S. officials said they had been promised access to Chen in the hospital, Britain’s Channel 4 news quoted a conversation with him in which he seemed confused and upset that no American diplomats were around.

“Nobody from the [U.S.] embassy is here. I don’t understand why. They promised to be here,” Channel 4 quoted Chen as saying.

Bob Fu, president of the advocacy group ChinaAid, said he was concerned that “the U.S. government has abandoned Chen” and that the Chinese government is “using his family as a hostage.”

Mufson reported from Washington. Washington Post researcher Zhang Jie in Beijing contributed to this report.