The U.N. Security Council says it is ready to "act immediately" if South Sudan's president doesn't sign a peace deal Wednesday.

President Salva Kiir shocked observers and rebels last week by refusing to sign after rebel leader Riek Machar did. Kiir said he needed more time to consider, but the United States called that "outrageous" and drafted a council resolution that would impose an arms embargo and targeted sanctions if he doesn't sign by Sept. 1.

Kiir's spokesman now says he is expected to sign Wednesday at a summit with regional leaders in the nation's capital, Juba.

Current council president and Nigerian Ambassador Joy Ogwu adds in her national capacity that "we all believe that an arms embargo would go a long way in eliminating the situation" on the ground.