New York — The United States is leading international warnings to Sudan and South Sudan to step up efforts to reach a peace accord this week or face possible UN sanctions.

The UN Security Council has given the rival neighbors, who this year came close to all-out war, until Thursday to make their peace.

Tentative talks are being held in Addis Ababa. Diplomats said however that while no accord is expected the 15-nation council will probably hold back from ordering immediate action.

"It appears increasingly unlikely that a comprehensive agreement on outstanding issues will be reached" by the August 2 deadline, said Susan Rice, the US ambassador to the United Nations.

South Sudan broke away from Sudan in July last year but no deal has ever been made to set their frontier, how to share revenues from oil reserves that straddle the border, or how to settle citizenship disputes.