RIYADH (AP) -- Sudan has signed a joint agreement with the United Nations and the African Union that defines their respective roles in Darfur, the official Saudi news agency reported on Sunday.

Sudanese President Omar al-Bashir phoned Saudi King Abdullah and told him the Sudanese government had signed the agreement, the SPA news agency reported.

It quoted the king as saying the agreement "will support Sudan's unity, security, stability and peace." No additional details were provided.

In New York, UN deputy spokeswoman Marie Okabe said she could not immediately confirm the Saudi report.

U.S. Deputy Secretary of State John Negroponte, in Sudan as part of an international push to increase pressure on the government over Darfur, avoided commenting on the report of an agreement.

Abdullah, along with UN Secretary-General Ban Ki-moon and Arab League chief Amr Moussa, met al-Bashir at an Arab summit in Riyadh last month to discuss the introduction of UN peacekeepers into Darfur.

More than 200,000 people have been killed and 2.2 million forced to flee their homes in the four-year conflict in Darfur, which began when rebels from ethnic African tribes rose up against the central government. The government is accused of responding by unleashing the janjaweed militias of Arab nomads — blamed for indiscriminate killing. The government denies the charges.

The United Nations and Sudan agreed in November on a three-stage plan to strengthen the undermanned and under-equipped AU peacekeeping force of 7,000 in Darfur. It was to culminate in the deployment of a joint AU-UN force with 17,000 troops and 3,000 police officers.

The first phase, a light support package including UN police advisers, civilian staff and additional resources and technical support, has already been sent to Darfur.

The UN, AU and Sudan agreed on a second phase last Monday — including more than 3,000 UN troops, police, and other personnel as well as substantial aviation and logistics equipment. But Sudan rejected a proposal to include six attack helicopters.

Al-Bashir has backed off from the final stage, saying he would only allow a larger AU force, with technical and logistical support from the United Nations. He maintains that deployment of UN troops would violate Sudan's sovereignty.

Negroponte was in Khartoum hoping to persuade the government to accept the larger third-phase force. His visit comes as the U.S. is holding off on imposing sanctions against Sudan so negotiations can take place on the proposal.

On Monday, Ban is to host a meeting at UN headquarters attended by AU negotiators to try to get a political agreement on Darfur.