The UN Security Council said it would take immediate, unspecified action if President Salva Kiir (above left) does not sign a deal to end a 20-month civil war in South Sudan.

Kiir is expected to sign the power-sharing agreement alongside regional leaders in the capital, Juba, on Wednesday, but has voiced hesitation through a presidential spokesman.

Spokesman Ateny Wek Ateny said Kiir would express reservations over the agreement, which rebel leader Riek Machar (above right) signed a week ago. Ateny said Kiir was unhappy about demands that Juba be demilitarized, among others.

"We will take immediate action if he does not sign, or if he signs with reservations," said the current UN Security Council president, Nigerian Ambassador Joy Ogwu.

The US has proposed an arms embargo and targeted sanctions on South Sudan if Kiir does not sign the accord.

The country has been torn by fighting between forces loyal to Kiir and rebels allied with Machar - Kiir's former deputy - since December 2013. The violence has escalated along ethnic lines. Thousands of people have been killed, and more than 1.6 million displaced.

The agreement commits both sides to a "permanent ceasefire" within 72 hours of signing. It also means Machar would likely return to his former post, as it gives rebels the post of first vice-president. Machar was sacked from the position in July 2013, six months before the fighting began.

jr/msh (AP, AFP)