The head of an international group monitoring South Sudan's peace process says the formation of a transitional national unity government in South Sudan "now seems within reach."

Festus Mogae told the U.N. Security Council on Thursday that despite continuing cease-fire violations "there has been notable progress."

South Sudan has been at war since December 2013 as government forces loyal to President Salva Kiir battle rebels led by his former deputy Riek Machar. They signed a peace deal in August 2015, but fighting has continued, even since Kiir named Machar to be his vice-president again on Feb. 11.

U.N. envoy Ellen Margrethe Loj said South Sudan "is at a critical juncture" and sustained progress requires both leaders to form the transitional government without delay.