BEIJING — Chen Guangcheng, the blind dissident lawyer at the heart of a diplomatic crisis between China and the United States, telephoned in to a Congressional hearing on Thursday to plead for help in leaving his country.

Via a cellphone held up to a microphone at the hearing, Mr. Chen, speaking in Chinese, said: “I want to come to the U.S. to rest. I have not had a rest in 10 years. I’m concerned most right now with the safety of my mother and brothers. I really want to know what’s going on with them."

Mr. Chen, according to the English translation of his comments, also asked to meet with Secretary of State Hillary Rodham Clinton, who was in Beijing. "I hope I can get more help from her," he said. "Also, I want to thank her face-to-face."

The call, apparently made from Mr. Chen’s Beijing hospital room from which American officials have been barred, was another dramatic turn in a case that had for a short time looked like a deft achievement to secure Mr. Chen’s safety by American diplomats. That achievement has unraveled, leaving the Obama administration open to attacks from rights activists and Republicans that it had failed to adequately protect Mr. Chen after he left the sanctuary of the United States Embassy here on Wednesday.