By Thomas Atkins

GENEVA, March 18 (Reuters) - U.N. and African peace envoys on Tuesday urged donor nations to speed support to peacekeepers in war-torn Darfur, and called on Chad and Sudan to work harder to cool border tensions exacerbating the long-running conflict.

"If we can get a quicker deployment of the peacekeeping troops then we can convey the message that yes, the security is increasing," said Jan Eliasson, the U.N. special envoy to Darfur.

"For peacekeeping to be successful there has to be a peace to keep," he told a news briefing at the close of two-day talks at the United Nations offices in Geneva.

Efforts to end the conflict in which some 200,000 people are estimated to have died have been dogged by tribal clashes, tensions between Chad and Sudan, divergent interests by the international community and fragmented rebel demands.

Darfur has been beset by unrest since early 2003 when mostly non-Arab rebels took up arms against Khartoum, accusing the central government of neglect.

A joint U.N.-African Union mission took over peacekeeping duties on Dec. 31, but with only 9,000 of the required 26,000 troops and police on the ground it has not yet been able to do its job properly.

Eliasson and Salim Ahmed Salim, the special envoy of the African Union for Darfur, met in Geneva with negotiators from Chad, Eritrea, Egypt, Libya and international observers to take stock of the region's needs. "We have been able to achieve some progress," Salim said.

Two of the five rebel groups in Darfur are ready to meet with the Sudanese government, one seeks more time and two others have placed security preconditions, the envoys said.

Most recently, the powerful Darfur rebel group JEM, or the Justice and Equality Movement, has demanded one-on-one peace talks with the Sudanese government, saying it was the only viable insurgent force.

CHAOTIC MIX

"There are rather far-reaching demands that we have to deal with," Eliasson said. "If they don't unify their own movements then we hope at least they will unify positions."

The government's response to the revolt -- the mobilisation of mostly Arab tribal militia -- coupled with rebel divisions has created a chaotic mix of armed groups and a breakdown of law and order.

Cross-border incursions between Chad and Sudan threaten to further complicate the search for peace, the envoys said.

The two countries accuse each other of supporting insurgents in Darfur and neighbouring eastern Chad. President Idriss Deby fended off a rebel assault on N'Djamena in February, which he accused Khartoum of organising.

Sudanese President Omar Hassan al-Bashir and Deby signed a non-aggression pact in Senegal late last week in an effort to end cross-border rebel attacks on their respective territories.

"For there to be sustainable peace in Darfur it is absolutely crucial that there be a normalisation of relations between Chad and Sudan," Salim said, also calling on Western governments to provide more logistical support to the mission.

International experts estimate 2.5 million people have been forced from their homes in the five years of revolt in Darfur, which borders Chad. Washington calls the violence genocide, a term European governments are reluctant to use and which Khartoum rejects. Sudan says only 9,000 people have died. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/ ) (Editing by Matthew Jones)

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