At least 2.4 million people have been displaced by the Darfur conflict

A UN report says Sudan painted aircraft white to make them look like UN planes.

Sudan's envoy to the UN, Abdel Mahmood Abdel Haleem, said the allegations were "a lie" and that military assets were simply being moved around the country.

The US and the UK will later begin talks with other Security Council members o­n a new resolution o­n Darfur.

Abdel Mahmood Abdel Haleem told the BBC: "According to the comprehensive peace agreement signed [after the civil war in the South] between the Sudan government and the SPLM, we have to move our military assets and aircraft and all assets from the South to other regions in the country.

UN DARFUR PLAN Phase 1 - UN financial backing for AU mission Phase 2 - UN sends logistical and military support Phase 3 - UN takes joint command of hybrid force

"We are moving these military assets to their respective places. We are not using these aircraft for any military function in Darfur."

But a New York Times journalist who has seen a leaked copy of the UN report says there is no doubt about the evidence.

"One thing is pictures that appeared with the report that we actually published in the New York Times today," Warren Hoge told the BBC World Service's World Today programme.

"There are very clear pictures of planes painted white, and also with the UN designation o­n the left-hand wing of o­ne of the planes. And also a good deal of testimony from the investigators who compiled the report.

"It's the credibility of the United Nations versus the credibility of the Sudanese authorities - and I think o­n that basis the United Nations report looks pretty good."

The report was compiled by a five-person panel for the Security Council committee monitoring sanctions against Sudan.

US sanctions warning

US Deputy Secretary of State John Negroponte ended his tour of Sudan and its neighbours o­n Wednesday, without meeting Libyan leader Muammar Gaddafi.

Mr Negroponte visited Sudan, Libya, Chad and Mauritania, hoping to increase pressure o­n Sudan to let more UN peacekeepers into Darfur.

President George W Bush has said he wants tougher sanctions if Khartoum did not accept 20,000 UN peacekeepers being sent to the region, a move opposed by Russia and China.

Mr Bush said he was giving UN Secretary General Ban Ki-moon o­ne last chance to reach a diplomatic solution.

Sudan said earlier this week it would allow 3,000 UN troops into Darfur to support 7,000 African Union troops, but has not agreed to a much larger force.