By Nick Childs
BBC Pentagon correspondent
A senior US general says a set of four special interrogation techniques have been used on two key detainees at Guantanamo Bay in Cuba.
About 600 people are being held at Guantanamo Bay
But he insisted the techniques conform to the Geneva Conventions and that all the prisoners are treated humanely.
The Pentagon previously acknowledged it approved interrogation techniques at Guantanamo Bay which go beyond the US military's normal practice.
It has insisted all the techniques conform to the Geneva Conventions.
This was a point underlined by the head of US Southern Command, General James Hill, whose responsibilities include Guantanamo Bay.
But Gen Hill has now said that four of the techniques require US Defence Secretary Donald Rumsfeld be notified, and that he can veto them.
The general said the techniques have been used against two key individuals held at Guantanamo Bay.
One prisoner is linked to the 11 September 2001 attacks on the United States, and another is described by General Hill as an al-Qaeda operative of high intelligence value.
Gen Hill insists that all prisoners at Guantanamo Bay are treated humanely and that he would not even call the additional techniques harsh.
However, the Pentagon refuses to say what the techniques are.
Against the background of the Iraq prisoner abuse scandal, the general's remarks are likely to raise new questions.