The United Nation's special investigator on torture says he can't accept the terms under which the United States has invited him to visit the Guantanamo Bay detention center.

Juan Mendez says he wants the U.S. to reconsider restrictions on his visit of the military prison on Cuba, including allowing him unmonitored conversations with detainees.

Mendez also said Wednesday he has been kept waiting for two years to visit prisons in the United States to probe the use of solitary confinement.

The U.N. expert wants to visit federal prisons — ADX in Florence, Colorado, and the Manhattan Correctional Center — and state facilities in California, New York, Louisiana and Pennsylvania.

Mendez says he hasn't been offered access to federal facilities yet and he isn't prepared to visit only state prisons.