By David Bamford BBC correspondent in at the UN

Del Ponte has led prosecutions at the court in Arusha since 1999

A UN spokesman confirmed that a letter had been forwarded to the Security Council by the Secretary General requesting this.

At the same time he is asking that her term as chief prosecutor for the War Crimes Tribunal on former Yugoslavia be extended for four years.

Mr Annan apparently wishes the two courts to operate separately, but there is more to this development.

We need someone who devotes adequate time to the affairs of the tribunal. Rwanda does not deserve second-rate justice. Rwanda Government prosecutor Gerald Gahima Del Ponte profile

Ms Del Ponte is known to personally oppose being taken off her Rwanda role and UN sources say she said as much at a late evening meeting on Monday with Mr Annan, but there has been unease at the UN about the length of time the Rwanda tribunal process has been taking.

Also the government of Rwanda has been at odds with Ms Del Ponte over her wish to extend prosecutions beyond the massacres carried out by Hutu extremists in the mid-1990s.