US Defence Secretary Donald Rumsfeld says he will not allow UN human rights monitors free access to detainees in the Guantanamo Bay prison camp.
A number of detainees are involved in a hunger strike
The monitors were invited to visit the camp by the Pentagon last week, three years after a request by the UN.
However, they said they would not visit the camp if a ban on private interviews with detainees remained in place.
About 500 people are held at the camp. To date, only the Red Cross has been granted direct access to prisoners.
Mr Rumsfeld said the US Government's position was to reject the monitors' request for free access because the Red Cross had "complete and total access".
"We're not inclined to add the number of people that would be given that extensive access," he said, the Associated Press news agency reported.
The Red Cross does not make its findings public in order to preserve its access to prisons that might otherwise be closed to them.
Mr Rumsfeld also dismissed the motives of a group of hunger-strikers at the camp.
Defense lawyers say as many as 200 detainees are involved in the protest over conditions.
"What they're trying to do is capture press attention, obviously, and they've succeeded," he said.
The UN first asked for permission to visit the camp when it opened in January 2002, months after the US-led invasion of Afghanistan which toppled the Taleban regime.
The UN has accused the US of stalling over its repeated requests to visit the camp to look into allegations of human rights abuses.