Sudanese President Omar Hassan Al-Bashir signed a ceasefire deal with the main Darfur rebel group on Tuesday that is intended to lead to a broader peace deal, a Reuters witness at the signing ceremony said.

Qatar's Emir, Sheikh Hamad bin Khalifa Al-Thani, whose country sponsored talks leading to the deal, said Qatar would contribute $1 billion to a fund to reconstruct Sudan.

Khartoum will offer Darfur's most powerful rebel group government posts as part of a future peace deal to end fighting in western Sudan, according to documents setting out the terms of negotiations that were seen by Reuters.

The documents were the first concrete sign that Khartoum is prepared to share power with its bitter foe in Darfur -- a development that could alienate existing allies there and complicate preparations for April elections.

Rebels of the Justice and Equality Movement played down the chances of reaching a final peace pact by March 15, as outlined in the framework deal for peace talks signed in Doha, capital of Qatar, the world's biggest liquefied natural gas exporter.   

"We are working to meet the March 15 deadline, but that itself is not a requirement," said chief JEM negotiator Ahmed Tugud, one of those who later signed the agreement.   

"We are trying to move forward, at least. It has been a long time since we've had a direct dialogue (with the government). We believe it is the right time to start," he told Reuters.

Another rebel official said the deadline was unrealistic, and rebels reported fresh violence in Darfur two days after an initial version of the framework peace deal was inked in Chad.

The initial framework included a ceasefire, plans to integrate the JEM into Sudan's army and a promise to reach a final peace deal by March 15. Tuesday's event was billed as the "official signing."    

According to a French-language copy of the framework accord, the JEM and Khartoum agreed to "the participation of the Justice and Equality Movement at all levels of government ... in a manner to be agreed subsequently between the two parties."    

UN Secretary-General Ban Ki-moon's press office issued a statement welcoming the deal, saying it was "an important step towards an inclusive and comprehensive peace agreement for Darfur, which will address the underlying causes of the conflict and the concerns of all Darfurian communities."    

It added that Ban hoped all provisions of the agreement would be fully implemented. 

It is a year since Khartoum and the JEM met in Doha to agree to confidence-building measures designed to pave the way for the framework agreement and then full peace talks. That process stalled after the JEM accused Khartoum of attacking its positions days after the ceasefire and of failing to carry out agreed measures, including freeing JEM captives.

JEM rebels, widely thought to control the biggest military insurgent force in Darfur, said on Tuesday they had been attacked by government forces on Monday in violation of the truce but would press on with signing the peace framework.   

Sudan's army denied being involved in clashes with the JEM, which carried out an unprecedented attack on Khartoum in 2008, and the rebel report was not confirmed by independent sources.

Khartoum has accused rebels of fabricating attacks in the past, but the timing of the JEM report could cast a shadow over ceremonies to ratify the ceasefire in Doha.

"Our comrades and garrison east of Jabel Moun (near West Darfur's border with Chad) were attacked by government forces and militias, backed up by Antonovs (aircraft) and helicopters ... we defeated them," said JEM spokesman Ahmed Hussein Adam.

A Sudan army spokesman said: "The Sudanese army is not involved in any clashes with JEM ... (It) is committed to the agreement between the Sudanese army and JEM."   -Reuters