Chen deal called a 'very big moment' for China

(CNN) -- The deal that led to Chinese dissident Chen Guangcheng leaving the U.S. Embassy is an unprecedented move for Beijing, U.S. and Chinese observers said Wednesday.

Chen has since expressed regret for accepting the proposal, telling CNN that he fears his life is now in danger. But Douglas Paal, a top China analyst at the Carnegie Endowment for International Peace, said the agreement that led to his departure was "unprecedentedly positive."

"The practical result in this case is spectacular," said Paal, a former State Department and CIA official. "Here's a guy who was being harassed extralegally by thugs, and that's stopped, and there's an international promise to back that up."

Chen Guangcheng: I want to go to the U.S.

Senior U.S. official on Chen Guangcheng

Chinese officials have guaranteed that no further legal issues will be directed at Chen and that reports of mistreatment against him will be investigated, a U.S. official said Wednesday.

Chen's impact on U.S.-China ties

In late April, the blind, self-taught lawyer evaded guards who had kept him under house arrest for more than 18 months in a village in the eastern province of Shandong. Chen, 40, had been confined to his home after serving four years in prison, apparently over his legal advocacy for what he called victims of abusive practices such as forced abortions by China's family planning officials.

Part 2: Case of the 'Barefoot Lawyer'

Dissident artist Ai Weiwei, who is under house arrest, called Chen's decision to return "a very symbolic moment and a very big moment."

"I think the officials cannot behave the same way anymore," he told CNN. "They have to do something. They have to do something to make a political change."

Escaped activist leaves U.S. embassy

Aided by friends and fellow activists who had raised concerns about his health, Chen made his way to Beijing and sought refuge in the U.S. Embassy for six days. This created a sticky situation with China less than a week before a visit by Secretary of State Hillary Clinton. He left Wednesday for a hospital after affirming to U.S. Ambassador Gary Locke that he was doing so voluntarily, Assistant Secretary of State Kurt Campbell told CNN.

Campbell said Chen decided to leave the embassy "after he knew his family was safe and at the hospital waiting for him." But once he had arrived at the hospital, Chen told CNN that he did not believe embassy officials fully informed him of what he faced before he walked out and that he now wants to leave his homeland.

Paal said Chen's reversal may be a way to put Beijing on notice "that whole world is watching you, and you'd better follow through on your promise and more." But Bob Fu, president of the U.S. Christian human rights organization ChinaAid, said Washington "has abandoned Mr. Chen" and his family.

"I think their safeties are still in jeopardy, in danger," Fu told CNN. "I would suggest Secretary Clinton visit him and his wife to listen to their concerns directly, and bring him back to the United States."

But Chen got "probably the best deal an individual Chinese dissident could get" with the help of U.S. officials, said Jamie Rubin, who served as assistant secretary of state in the Clinton administration.

"I suspect, as is usually the case in these things, there was a little bit of gray," Rubin said. "U.S. officials probably did have to make clear to them that they don't run China, the United States is not in a position to dictate to China how to treat its citizens. But I think what he got, which no other dissident in modern memory has got, was an American official at the level of secretary of state or assistant secretary of state basically pursuing over many days the terms of his ability to live in China in as much freedom as possible."

The dispute "certainly took up a lot of time for the top officials -- Secretary Clinton, but in particular the assistant secretary of state -- instead of trying to work on other subjects related to the economy or North Korea or Syria or Iran," he said.

Rubin said the issue is unlikely to have a long-term effect on U.S.-Chinese relations, he said. But Paal said the United States can't allow its diplomatic posts to become a haven for dissidents, "otherwise we're interfering in China's internal affairs."

CNN's Matt Smith contributed to this report.