UNITED NATIONS –  The U.N. Security Council is warning South Sudan’s feuding president and ex-vice president that it is ready to impose an arms embargo and sanctions if they don’t immediately stop fighting and implement a new peace agreement.

A presidential statement approved Friday was aimed especially at President Salva Kiir, who signed the deal Wednesday with reservations.

Rebel leader Riek Machar signed on Aug. 17. The council quickly threatened sanctions after Kiir refused to sign at the time.

The statement welcomes the signatures but expresses concern “with any statement by any party suggesting a lack of commitment to implement the agreement.”

Fighting broke out in the world’s newest nation in December 2013 after Kiir accused Machar of trying to oust him. The violence has killed thousands and displaced over two million people.