The United States is criticizing South Sudan's government for refusing to sign a peace deal by yesterday's deadline.

At the United Nations, U.S. deputy ambassador, David Pressman, called it "outrageous" that South Sudan President Salva Kiir declined to sign a peace agreement with rebel forces.

Kiir said Monday he needs another 15 days to sign, Mediators said rebel leader Riek Machar signed the accord.

Both the U.S. and Britain say the U.N. Security Council must act to pressure those preventing an end to the conflict that has killed thousands.

But neither of the permanent council members mentioned further sanctions in their statements Tuesday.

South Sudan has been at war since December 2013, and multiple attempts at a peace agreement have failed.

In July, the Security Council imposed sanctions on six generals for fueling the fighting.