Dissident Chinese activist Chen Guangcheng who arrived in the United States in May, has urged Washington to investigate his case and to protect the members of his family who remain in China.
Mr Chen said guarantees given to him by Beijing had not been adhered to.
Mr Chen, 40, escaped house arrest and fled to the US embassy in Beijing in April. He arrived in the US with his wife and two children in May after negotiations.
The BBC reports he has expressed concerns about friends and family left behind.
A nephew, Chen Kegui, has reportedly been arrested and charged with manslaughter after a dispute with officials who came looking for Mr Chen following the escape from house arrest.
''The Chinese central government explicitly promised me that it would thoroughly investigate the extended oppression and abuse that I endured in Shandong province,'' Mr Chen told a news conference in Washington on Wednesday.
''The government further promised to provide for the security of my family. However, it has been more than three months and I have not received any news on the progress of this investigation or even whether it has commenced,'' he said.
Mr Chen was sentenced to more than four years in prison in 2006. He was released in 2010 but later put under house arrest.
Chinese authorities have allowed him to leave the country to study at New York University School of Law.