The African Union is warning two Sudanese rebel factions to sign the Darfur peace accord or face international sanctions.

The chairman of the A.U., Alpha Oumar Konare, urged the two groups to sign the accord unconditionally.

Konare said Monday the A.U. will ask the United Nations Security Council to impose sanctions on anyone who undermines the peace deal.

Sudan's government and the largest rebel group, the Sudanese Liberation Movement, signed a peace agreement on May 5, designed to end three years of conflict in Sudan's western Darfur region.

Meanwhile, United Nations Secretary-General Kofi Annan has asked Sudan's President, Omar Hassan al-Bashir, to allow a U.N. assessment team into Darfur to begin planning the logistics for replacing A.U. troops with U.N. peacekeepers.

In an article in The Financial Times, Mr. Annan said the U.N. force would be larger, better equipped and have a stronger mandate than the A.U. forces currently in the region.

Some information for this report was provided by AP and Reuters.