The U.S. government has joined a growing list of international agencies calling on authorities in Guyana to immediately revoke radio frequencies issued to those closely connected to the South American country's ruling party.

Last month, legislators forced Prime Minister Samuel Hinds to release the list of those allocated frequencies in 2011. It showed the governing party gave itself five frequencies, five to the sister of Cabinet Minister Robert Persaud and five to the best friend of former President Bharrat Jagdeo.

U.S. Ambassador Brent Hardt said Guyana should "promptly review and approve" pending requests from those qualified to operate radio stations. Some requests date back to the late 1990s.

Hardt made the request late Thursday and joined others who have voiced similar concerns, including the Vienna-based International Press Institute.