OSLO - Norwegian and Swedish army engineers could be in Sudan's Darfur region as early as November as part of the U.N.-AU Darfur peacekeeping mission, their commander says, but so far their offer has yet to be accepted.

If the African Union approves the 400 Nordic troops, they will be the largest and best-equipped contingent from the developed world in the 26,000-strong hybrid AU and United Nations force, the bulk of which will be African infantry.

Norway's Lieutenant-Colonel Anstein Aasen said the contingent's main role would be building bases for the rest of the force along with heavy engineering projects such as roads.

But despite being on four months' deployment notice since September 2006, they still had no firm word on if they were wanted.

"We hear rumours that we are welcome," he told Reuters this week at Norway's Defence Ministry.

"But nothing certain. It is extremely frustrating, not just for us but also for our families."

Observers say it is unclear if the delay in accepting the offer of the joint Swedish-Norwegian engineer battalion is due to opposition from Sudan's government, which wanted an all-African force, or from the African Union.

"My feeling is that eventually they will be accepted," said former U.N. aid chief Jan Egeland, head of a Norwegian foreign policy think tank. "But we are losing time. This force should have been on the ground four years ago."

International experts say some 200,000 people have died in Darfur since mainly non-Arab rebels took up arms against the government in 2003. The United States says Arab militia mobilised by Sudan have committed genocide, a term European and African governments have avoided.

Sudan says only 9,000 people have died. A small, poorly equipped African Union force has failed to stop violence.

At the weekend, 10 African Union soldiers were killed and 10 injured in a suspected rebel attack on an AU base in Darfur, the most serious assault on the force since it deployed in 2004.

If the Swedes and Norwegians are accepted, they will be the best-fitted battalion in the force, with more than a dozen Finnish-built wheeled armoured personnel carriers while most of the AU troops will be limited to land cruisers.

Aasen said the battalion would stick to engineering and leave civilian protection to the African infantry. But he said his troops would fight to defend people in danger if necessary.

Serious problems, however, must be resolved before his troops can deploy, he said.

Even if the U.N. and AU give the green light, the force currently has too few helicopters to offer 24-hour medical evacuation cover -- a pre-requisite for Norway to send troops.

Aasen, who first visited Darfur last month, said he was looking forward to the mission -- but not the weather.

"It will be very, very hot," he said. "It is the worst weather possible for a Norwegian."