A major Darfur rebel group has reached a "framework agreement" with the Sudanese government, according to news agencies and the United States government.

In a statement issued by the U.S. State Department on Monday, spokesman Philip J. Crowley described the deal as "a significant move toward formal negotiations" in the peace process which is being driven by the African Union and the United Nations.

Reuters news agency reported from Khartoum Tuesday that it had seen documents showing that Sudan will offer government posts to the Justice and Equality Movement (JEM) as part of the deal.

But an Al Jazeera correspondent, reporting from Doha, Qatar – where a formal agreement was scheduled to be signed on Tuesday – said the JEM might assume an opposition role.

The news outlet quoted its correspondent as saying that "JEM looks like it's repositioning itself in Sudanese politics to become an important political player – either in the government or perhaps as a leading opposition group."

Agence France-Presse reported President Omar al-Bashir as saying at a meeting in Doha that the agreement "marks the start of the end of the war in Darfur."

The framework agreement and a ceasefire was first signed by the JEM's leader, Khalil Ibrahim, and Sudanese officials in Chad last weekend. President Idriss Déby Itno of Chad has played an important role in the peace process.

In Washington, the State Department said the ceasefire was "an important first step toward reducing violence in Darfur… We encourage all parties to the conflict to continue working toward a comprehensive agreement that includes the other major armed movements and civil society representatives."

In recent weeks, a major Sudanese lobbying coalition in the United States has been strongly critical of the role played by President Barack Obama's special envoy to Sudan, Major General Scott Gration.