After a daring escape, four grueling days of secret negotiations and a deal struck between the world’s two leading powers, blind activist Chen Guangcheng found himself isolated in a central Beijing hospital on Friday as Chinese guards barred U.S. diplomats, journalists and supporters from seeing him.

In a telephone interview early Friday, Chen said he does not blame American officials for his plight after leaving the U.S. Embassy under a deal they helped strike. But he accused Chinese officials of reneging on their promises to fully restore his freedom.

A few hours later, he made a dramatic call into a congressional hearing, telling lawmakers in Washington through the cellphone of a human rights activist that he wanted to travel to the United States to rest and that he was most worried about “the safety of my mother and my brothers.”

Chen said he wanted to travel to the United States, but only temporarily, perhaps to study. “It’s not a one-time-only decision,” Chen told the Washington Post from his hospital room. “It doesn’t mean I won’t come back. As a free person, I believe I am endowed with the right to leave China when I want to and come back anytime I want.”

China’s foreign ministry said Friday that if the well-known activist wanted to leave the country to study, he had to apply through the Chinese government like other ordinary citizens.

“Chen Guangcheng is currently being treated in hospital,” the spokesman, Liu Weimin, said in a statement. “If he wants to study abroad, he can apply through normal channels to the relevant departments, according to the law, just like any other Chinese citizen.”

With the fate of Chen and his family uncertain, the Obama administration drew sharp criticism Thursday for its handling of the crisis.

U.S. officials expressed concern and frustration at not being able to meet with Chen. But granting him any assistance — much less safe passage to the United States — has grown far more complex and difficult since his departure from the U.S. Embassy on Wednesday, six days after escaping de facto house arrest in his village.

Once Chen left the sovereign soil of the embassy, the leverage of U.S. officials went with him. Now he is under the control of Chinese authorities, who on Thursday blocked all access to the activist.

“We haven’t had either a diplomat or a doctor in to see him,” said one U.S. official, who spoke on the condition of anonymity to be more candid. “There’s plenty of anxiety about what’s going on.” The official said that U.S. diplomats had extraordinary difficulties even trying to telephone Chen on Thursday and that their two calls with him were extremely brief, with one cut off after just seconds. Lacking direct access to Chen, U.S. officials met his wife, Yuan Weijing, outside the hospital.

A senior State Department official said U.S. Embassy personnel again spoke with Chen and met with his wife late Friday morning.

According to U.S. officials, Chen had previously insisted that he wanted to remain in China. But U.S. Ambassador Gary Locke said Thursday that “it’s apparent now that he’s had a change of heart.”

Chen, in the interview, clarified reports portraying him as pleading for asylum, insisting that he wants to travel to the United States only temporarily, retaining the freedom to return to China.

Some Republicans and human rights advocates have accused the Obama administration of mismanaging Chen’s case, saying it was too trusting of the Chinese government, given its history of mistreating dissidents.

“Our embassy failed to put in place the kind of verifiable measures that would have assured the safety of Mr. Chen and his family,” said Mitt Romney, the presumptive Republican presidential nominee. “If these reports are true, this is a dark day for freedom, and it’s a day of shame for the Obama administration.”

‘Substantial’ fallout

For China, the crisis falls into an ongoing struggle between increasingly visible reform-minded moderates within the Communist Party and hard-liners who emphasize security and stability at any cost.

Some analysts saw Chinese officials’ quick acceptance of Wednesday’s deal as a sign of the reform faction’s sway. In many ways, China’s apparent willingness to give assurances to a foreign country about how it would treat one of its citizens was exceedingly rare.

But the deal’s rapid unraveling could, instead, boost hard-liners.

“The collateral damage here is substantial,” said Kenneth G. Lieberthal, a China expert at the Brookings Institution in Washington. “If there was a debate on the Chinese side on whether to negotiate, this certainly isn’t good for those who pushed for the deal.”

At the hospital Thursday, police harshly treated journalists and a small number of Chen’s supporters who tried to see him in his first-floor room. On Friday, more supporters reported being beaten and detained by police for going to the hospital to try to visit Chen.

Security officials also reportedly took away government-issued press cards from some journalists who tried to enter the hospital. On Friday, police were taking down the names and press card information from reporters who gathered outside the hospital.

Du Yanlin, an accountant and tax consultant for the dissident artist Ai Weiwei, said he tried to visit Chen around 1 p.m. Thursday but was turned away by plainclothes police officers. After he and his friends posed for a photo in front of the hospital wearing sunglasses like Chen’s, Du said, police followed him home and questioned him for “making trouble.”

Jiang Tianyong, a human rights lawyer, described in an interview how he went to Chaoyang hospital to try to see Chen around 6 p.m. Thursday, but was immediately hustled into an unmarked car by about 10 plainclothes officers from Beijing’s Haidan district public security branch.

Jiang said the agents took him to a hotel room where they first repeatedly insulted and berated him, and then one “suddenly jumped on me and punched me heavily three times, on my left ear, my right ear and my chest. I instantly felt a severe hearing loss.”

Jiang said he could barely hear, but they told him “The Chen Guangcheng incident is a big matter, not a small matter.”

Jiang said the policemen refused his repeated requests to go to a hospital; instead, they made him strip from the waist up and stand in the cold air of an air conditioner turned on full blast. He said he was taken home only around 3 a.m. Friday, and is now under effective house arrest with a police car parked outside his apartment with four or five officers waiting.

Apparent change of heart

Chen’s case overshadowed Thursday’s opening of a two-day U.S.-China summit that included Secretary of State Hillary Rodham Clinton and Treasury Secretary Timothy F. Geithner.

Both sides were careful not to mention Chen’s case specifically. But from his isolated hospital room, Chen still managed to thrust himself into the center of the stage-managed diplomacy when he told interviewers that he wanted to fly to the United States with Clinton when she leaves Saturday. U.S. officials and analysts, however, said privately that that appeared unlikely, given the significant political, diplomatic and legal hurdles, including Chen’s lack of passport or visa.

The activist’s apparent change of heart about where he wants to live has made the tense diplomatic episode especially difficult. More details emerged Thursday about what might have prompted his abrupt shift.

From the time he entered the fortified U.S. Embassy compound on April 26, Chen insisted that he wanted to remain in China and be reunited with his wife, said Locke and other officials. Under the original deal reached with Chinese officials, according to U.S. diplomats, the self-taught lawyer was to be allowed to move his family to the Beijing area and begin a new life as a university student.

But after Chen was taken in an embassy van to Chaoyang Hospital, he had his first extended telephone conversations with friends and allies, as well as his attorney, Teng Biao. Teng later posted the transcript of his Wednesday conversation with Chen on his Twitter account, in which he told Chen about the arrest of his relatives and some activists who aided in his escape from his farmhouse in Shandong province. Teng then asked Chen whether any U.S. diplomats remained with him at the hospital.

“No, they’ve all gone,” Chen replied, according to the transcript. “They said they would accompany me all the way, but now they’ve all gone.”

Teng said, “Then you’re in a really dangerous situation!”

In his brief interview early Friday, Chen sounded relaxed and full of energy — a sharp contrast to interviews Thursday, when he was reported to have sounded frightened. He said that he was being treated well at the hospital and that he, his wife and their two children were left alone together in one room.

But he said armed thugs have taken over his farmhouse in Dongshigu village, and he was concerned about other members of his family, with whom he has not been able to speak.

“My biggest wish right now is that the agreement concerning me is fulfilled well,” Chen said. “The agreement includes more than three points, including the U.S. side being able to visit me regularly, and China should guarantee my rights as a citizen.”

Authorities crack down

Rights activists say the moves to isolate Chen and round up activists who assisted him suggest that Chinese authorities never intended to honor their agreement to treat Chen humanely and allow him to live freely in a new and safe location in China.

Instead, many of his supporters have been harassed, and there has been a near-total blackout of all references to Chen on China’s popular Twitter-like microblogging sites. Even his initials, “CGC,” and terms such as “blind man,” the name of his town, “Linyi,” and even the prison escape movie “The Shawshank Redemption” were banned Thursday.

Still, some of Chen’s supporters made their way to the hospital. Liu Caiping, 38, said she arrived just after noon Thursday and was accosted by a plainclothes guard, who seized her cellphone.

“I’ve never seen Chen Guangcheng. I just heard about him last year,” she said. “It’s quite upsetting to see all the people who struggle for human rights in China are all getting forced out. He can play a bigger role in China.”

She then took out a pair of sunglasses like Chen’s and had her picture taken as a show of support.

Staff writers Jia Lynn Yang and Emily Heil and researchers Zhang Jie and Liu Liu in Beijing contributed to this report.