UN chief Ban Ki-moon has thanked Rwanda's President Paul Kagame for keeping peacekeeping troops in Sudan, despite anger over looming genocide accusations against the Rwandan army.

Rwanda had threatened to pull out of all UN peacekeeping operations because of a UN human rights report, due to be released on Friday, on the Democratic Republic of Congo (DRC).

Kagame's government is furious because a draft of the report alleged the Rwandan army carried out genocide-style slaughters of tens of thousands of ethnic Hutus in the DRC in the 1990s.

But the head of UN peacekeeping operations, Alain Le Roy, said Kagame had agreed to keep the approximately 3,500 Rwandan troops in international operations, including about 3,200 serving in the troubled Sudanese region of Darfur.

Ban met Kagame on Sunday on the sidelines of the UN General Assembly.

"The secretary-general said he was very satisfied to learn that Rwanda would continue its important role in peacekeeping, especially in Darfur," a Ban spokesman said in a statement, noting the two men discussed the DR Congo report.

The joint UN-African Union force is currently led by a Rwandan general and a withdrawal would be a major blow to peacekeeping efforts in Sudan, with a new rise in violence reported in recent weeks.

Ban went on a special surprise trip to Rwanda earlier this month in a bid to ease Kagame's anger over the report, which the president has decried as "absurd" and "fraudulent," and to get him to lift the threatened troop withdrawal.

In a face-saving move, the United Nations delayed the release of the report for one month and agreed to let countries named in it to add their comments to be published at the same time.

Kagame led the rebel group - the Rwandan Patriotic Front, RPF - that ended the 1994 genocide when up to 800,000 Tutis and moderate Hutus were slaughtered in massacres carried out by Hutu extremist militias.

Seven countries are named in the report, and Burundi has also demanded that it be removed from the final version.

The draft report had also accused the Burundi army of the 1990s and allied rebels of committing atrocities against civilians in DR Congo.