The Chinese human rights activist at the center of a diplomatic crisis a year ago on Tuesday accused Beijing of reneging on the agreement that freed him and urged the United States to intervene.

Chen Guangcheng, a blind self-taught lawyer who infuriated authorities by exposing forced abortions, dramatically escaped house arrest in April 2012 by scaling the walls of his home and taking a getaway car to the US embassy.

China allowed Chen to leave in May for the United States after protracted negotiations. But Chen charged that Beijing violated promises in the agreement to ensure his family's safety and to investigate the past abuses.

In an interview with AFP, Chen voiced anger over a prison sentence handed in November to his nephew, Chen Kegui, who the activist said had been severely beaten as retaliation for the escape that made headlines around the world.

"Not only has the Chinese government not fulfilled its own promises to me a year ago, but it has also become worse as they have not stopped persecuting my family members," Chen said.

"This in itself shows that the Chinese communist regime has no intention to change its course," he said.

The activist called for the United States to release the diplomatic records of last year's negotiations and to raise the agreement with China.

"The United States should make this clear publicly, demanding that the Chinese government fulfill its promises in the agreement with the US," Chen said.

Chen entered the safety of the US embassy in Beijing on the eve of a visit by the then secretary of state Hillary Clinton, overshadowing annual talks between the United States and China.

China eventually allowed Chen to leave with his wife and son for New York to study law. Cynics said that China was hoping that a thorn in its side would fade into irrelevance overseas and that Beijing would never allow him back.

"This is no longer a problem in the age of the Internet and the 'global village,'" Chen retorted. "We can do a lot of things no matter where we are, so long as we pursue them."

"I really haven't even settled here in the US so this isn't the time to think about returning. But there is no doubt that in the future, I will be able to travel to China and travel with full freedom," he said.

Chen was in Washington to testify before the House Foreign Affairs Committee. It was his first in-person appearance before the committee, which he addressed by telephone last year during the crisis to voice fear for his safety if he stayed in China under an initial accord.

Also testifying before the committee was Geng He, the exiled wife of jailed human rights lawyer Gao Zhisheng, who urged renewed international pressure on China to release her husband and other dissidents.

Chen just a year ago had spent little time outside a small area of eastern Shandong province, where he documented the forced abortions or sterilizations of up to 7,000 women under China's one-child policy.

A wiry 41-year-old who was still visibly nervous answering questions, Chen said he has generally had a smooth transition to student life at New York University -- located in bohemian Greenwich Village.

"The feeling of sunshine is what really struck me in the United States," Chen told AFP after reflection.

"It reminded me of when I was a few years old back in China. This really shows that environmental pollution has reached an intolerable level," Chen said.

An autodidact who has been blind from birth and speaks little English, Chen said that he has viewed society in different ways since studying the Constitution and other foundations of US law.

"In America, as long as you're not in violation of the law, you can do anything. In China, even if what you do benefits all people in society and is in accordance with the letter of the law, you can be persecuted if the party leader isn't happy," he said.

With his time devoted to study and advocacy, Chen said that he has generally had little time to relax.

But one exception came in January when, in a scene unthinkable months earlier, Chen went to Disneyland with Christian Bale. The actor had tried but failed to visit the activist when he was under house arrest to publicize his plight.

"Christian Bale isn't only acting as Batman, he is Batman in reality," Chen said with a laugh.