KHARTOUM - U.N. and African Union peacekeeping troops in Darfur must respond with force if attacked by armed groups, British parliamentarians said on Wednesday.

The current 7,000-strong African Union force in Darfur has failed to stem violence in the region despite a 2006 peace deal.

Western countries hope the joint peacekeeping force of 26,000 troops will bring an end to 4-1/2 years of conflict which has killed 200,000 people and driven 2.5 million from their homes.

"What the people are asking for is to make a difference on the ground," said MP David Drew, chair of the British parliamentary group on Sudan.

"Either they say okay we'll wait and push somewhere else or they really do take them on and they say sorry we're going to disarm you," he said.

Susan Kramer, a member of parliament for Richmond Park, said the force could not be a soft target.

"If they are seriously challenged they will have to respond ... it has to be with force," she said.

"The hybrid force will have to show that it's utterly determined and show that it will not tolerate attacks on the force or attacks on vulnerable people," she added.

Mostly non-Arab rebels took up arms in early 2003 accusing central government of marginalising the remote west. Khartoum mobilised militias to quell the revolt.

Ahead of peace talks due to begin in October, AU and U.N. mediators are trying to bring several different rebel groups to a unified platform. But Sudan Liberation Army (SLA) founder and chairman Abdel Wahed Mohamed el-Nur has refused to join the talks until international forces have secured Darfur.

Drew said France, who is hosting Nur, should advise him to either return to Darfur or go to the talks.

"If he's a serious player he hasn't got a more important time to be around than now," he said. "He ought to be doing something because just staying in Paris isn't helpful to anybody."

Darfur's conflict has spread across borders to Chad and the Central African Republic (CAR). Presidents from both nations have accused Sudan of supporting rebels trying to overthrow their governments.

Late on Tuesday, CAR President Francois Bozize visited Khartoum in an apparent rapprochement. A European Union force has been suggested to patrol the Chad-CAR-Sudan border to prevent cross-border attacks by armed groups.

"It's not in the interests of Sudan to disrupt the stability and security in your country or in any other country," said President Omar Hassan al-Bashir after the talks.

"We are totally convinced that we can bilaterally ensure a successful security and stability situation in the area more than any foreign forces," Bashir said.