U.N. officials have said the 26,000-member U.N./African Union force now being deployed cannot work effectively to end the 5-year-old conflict in the west Sudanese region, which is as big as France, without transport and attack helicopters.

Despite intensive lobbying by U.N. Secretary-General Ban Ki-moon and other top officials, countries had been reluctant to offer the craft until Ethiopia and Bangladesh -- both already supplying ground troops for the U.N./AU Mission in Darfur, or UNAMID -- recently stepped forward.

On Thursday, a U.N. official said Ethiopia had offered six attack and transport helicopters and Bangladesh five transport helicopters. That would still fall short of the total U.N. request for six attack and 18 transport helicopters.

But the official, who spoke on condition of anonymity, said: "The Bangladeshi kit will not meet our requirements, but the Ethiopian stuff will and we will ask for more."

Problems with the Bangladeshi offer included inadequate range and inability to fly at night, he said.

Jane Holl Lute, a senior official in the U.N. peacekeeping department, told a news conference on Thursday, "dialogue with Bangladesh continues."

On Ethiopia, she said: "I think part of that offer is seen as suitable," but declined to say when any helicopters might arrive in Darfur.

Helicopters aside, the UNAMID deployment, agreed by Sudan in mid-2007, has been delayed by disputes with Khartoum over rules governing its presence and over which countries can contribute troops. Some 9,000 soldiers are currently in place.

International experts say the Darfur conflict among Sudanese forces, pro-government militias and Darfur rebel groups has killed 200,000 people and made over 2 million homeless. Sudan says the figures are much lower.