By Louis Charbonneau

UNITED NATIONS (Reuters) - Sudan has violated an embargo on arms transfers to its war-torn Darfur region and disguised planes to look like U.N. humanitarian aircraft, the U.S. envoy to the United Nations said on Tuesday.

Speaking at a meeting of the U.N. Security Council on Darfur, U.S. Ambassador Zalmay Khalilzad accused Khartoum of a litany of duplicitous actions, all of which he said had been documented by an expert panel of the U.N. Sanctions Committee.

They included "violating the limited arms embargo on Darfur, using aircraft painted to resemble U.N. humanitarian aircraft, (and) conducting offensive overflights in Darfur."

He also accused Sudan of "not accepting that there is no impunity for war crimes and crimes against humanity" -- a reference to Khartoum's refusal to hand over two men indicted by the International Criminal Court for mass murder in Darfur.

Sudan's U.N. Ambassador Abdalmahmoud Abdalhaleem dismissed the allegations, adding that the charge about painting aircraft to look like U.N. planes had been recycled from a year ago.

Separately, a top U.N. peacekeeping official said that her department had revised its forecast for the deployment of U.N.-African Union peacekeepers in Darfur, known as UNAMID.

The U.N. under-secretary-general for field support, Susana Malcorra, told the council that her new targets assumed that 60 percent of UNAMID's full mandated strength of 26,000 would be deployed by the year's end.

The new U.N. peacekeeping chief Alain Le Roy had said last month he expected only half would reach Darfur by December 31.

NEW TARGETS

Malcorra said a previous U.N. goal of 80 percent of full UNAMID deployment by the end of this year had been unrealistic. That would be reached by the end of March 2009, she said.

"These new revised targets reflect a scaling back of initial extremely ambitious projections," she said. "The new targets are still ambitious but in our view can be achieved."

The United States complained for months about the slow deployment, blaming it on Sudanese obstructionism and U.N. bureaucracy. But Washington's special envoy to Sudan Richard Williamson told Reuters he welcomed the revised targets.

"We're encouraged that we should have at least 3,600 more UNAMID troops in Darfur by the end of this year," he said.

Abdalhaleem rejected the idea that Khartoum was doing anything to impede UNAMID's deployment. "The government of Sudan has been trying to remove all obstacles," he said.

U.N. officials have dismissed suggestions that they have moved slowly with the deployment of UNAMID, which was created in July 2007. They accuse troop-contributing countries of not providing badly needed military hardware like helicopters.

The council also discussed U.N. Secretary-General Ban Ki-moon's new report on UNAMID, in which he says up to 300,000 people have been forced to flee violence in Darfur this year.

Le Roy told the council he was especially worried about escalating violence in North Darfur, which he described as "deeply disturbing."

According to U.N. estimates, a recent increase in violence in North Darfur alone has displaced at least 40,000 people.

U.N. officials say that as many as 300,000 people have died and some 2.5 million fled their homes since violence broke out in Darfur in 2003, when mostly African rebels took up arms against the Arab-dominated Khartoum government.

The Sudanese government says 10,000 have died