Chinese activist Chen Guangcheng says he has been unable to meet US officials to discuss his desire to leave the country.
The blind dissident, in hospital in Beijing, says he believes Chinese officials were preventing US envoys from visiting him on Thursday.
After he escaped house arrest last week, Chen Guangcheng spent six days in the US embassy before emerging on Wednesday.
The issue continues to overshadow key talks between the US and China.
US Secretary of State Hillary Clinton is in Beijing to attend talks focusing on North Korea and Syria.
As the talks opened, Hillary Clinton did not mention Chen Guangcheng by name but addressed the topic of human rights.
Earlier, the US ambassador to China, Gary Locke, rejected the suggestion that Chen Guangcheng had been pressured into leaving the US embassy.
“I can tell you unequivocally that he was never pressured to leave. He was excited and eager about leaving,” he said.
However, Chen Guangcheng says since he left he has been made aware of threats made to his wife and family while he was in the embassy.
“She told me our house has been installed with seven CCTV cameras inside the courtyard. There are people in and outside of our house and on the roof…They just eat and stay in our house, and they plan to build up electric wires around my house,” he said.
Although he initially said he wanted to stay in China, Chen Guangcheng changed his mind because he believes China has reneged on an agreement to guarantee his safety.
There is no official confirmation about the nature of any such agreement, but media reports from the US suggest that Chen Guangcheng had been promised safety in a university town elsewhere in China.
Chen Guangcheng also said that US officials had been to the hospital where he is currently receiving treatment, but he had not seen them. He believes Chinese foreign ministry officials are not letting them in.
“Yesterday afternoon I thought they [US officials ] left. I looked for them, but couldn’t find them…Today I got to know that they were prevented from coming in, not that they are not coming in,” he said.
A Chinese foreign ministry spokesman said he had “no information” on Chen Guangcheng’s request to leave China.
Both Hillary Clinton and US Treasury Secretary Timothy Geithner are attending the annual two-day talks, which had been expected to focus on North Korea and Syria.
Hillary Clinton has previously expressed her support for Chen Guangcheng, who has been held under house arrest for almost two years.
As the talks opened, she addressed the topic of human rights.
“The United States believes that no state can legitimately deny the universal rights that belong to every human being – or punish those who exercise them,” the top US diplomat said.
President Hu Jintao, also speaking at the start of the talks, said it was not possible for China and the US to see “eye to eye on every issue”.
Chinese officials on Wednesday accused the US of interference in their domestic affairs and demanded an apology for housing Chen Guangcheng at the embassy.
Chen Guangcheng had been at the US embassy for almost a week after escaping from house arrest in his home village in the eastern province of Shandong.
He had planned his escape from house arrest for months. On 27 April, he scaled the wall the authorities had built around his house and was then driven hundreds of miles to Beijing.
The activist spent seven years in prison or under house arrest after he exposed human rights abuses, including the way thousands of women were forced to have abortions under China’s “one-child-policy”.
Several people involved in Chen Guangcheng’s escape have been detained or have disappeared in recent days.