The United States is seeking the swift transfer of a Congolese warlord from its embassy in Rwanda to a war crimes tribunal for a trial that could help eastern Democratic Republic of Congo inch towards peace.

Bosco Ntaganda gave himself up to the US Embassy in Kigali on Monday after a 15-year career leading Rwandan-backed rebellions in eastern Congo.

He asked to be sent to the International Criminal Court (ICC) in The Hague, where he faces war crimes charges. However, the trial could take months or even longer to start.

Mr Ntaganda's departure from the conflict zone, where he was a leading commander in the M23 group fighting Congolese forces, could improve prospects for stability in a region where vast mineral resources have fuelled two decades of conflict.

But the trial of Rwandan-born Mr Ntaganda could also prove an embarrassment to the Rwandan Government, which has denied charges by a United Nations panel it backed the M23 rebels.

"This is an opportunity to advance a little bit of peace and stability in the eastern Congo," said Johnnie Carson, US assistant secretary of state for African affairs.

He also said Rwanda could use the opportunity to demonstrate its commitment to a February deal that called for regional states to help end conflict in Congo.

He said the Rwandan Government had offered "appropriate assurances" it would not interfere in the process of transferring Mr Ntaganda.

ICC Prosecutor Fatou Bensouda said the court was working closely with those on the ground to ensure Mr Ntaganda was transferred as quickly as possible. "It's logistics now ... a couple of days," she said, adding that court procedures meant the start of the trial would take time. "I can't speak for the judges, but in my experience three months minimum."

Mr Ntaganda faces charges of recruiting child soldiers, murder, ethnic persecution, sexual slavery and rape during the 2002-3 conflict in northeastern Congo's gold-mining Ituri district.

His whereabouts had been unknown after hundreds of his fighters fled into Rwanda or surrendered to UN peacekeepers at the weekend following their defeat by a rival faction of M23 rebels in eastern Congo.

Mr Ntaganda and his faction were seen as an obstacle to a peace deal between the M23 and the Congolese Government. Jason Stearns of the Rift Valley Institute, a research body working in the region, said he might have feared being sold out.

His decision to give himself up may improve the prospects for a deal with the M23 faction he opposed.

Mr Ntaganda grew up in Congo before fighting alongside Rwandan Tutsi rebels who seized control of the small central Africa country, ending the 1994 genocide in which more than 800,000 people died.

For Rwanda, the worries of being implicated by Mr Ntaganda may be outweighed by the desire to avoid being seen as seeking to protect an ICC indictee.

"It's possible the Rwandans will be nervous about what he might say if he got on the stand in The Hague," said Ben Shepherd, an analyst at Chatham House, a London-based international affairs institute.

However, Mr Shepherd said Kigali might be confident it could avoid being implicated, or might simply be hoping it would be years before he stood trial.