By Michelle Nichols

UNITED NATIONS (Reuters) - The United States proposed on Thursday that the U.N. Security Council renew a peacekeeping mission in South Sudan for 10 days while the body considers clamping an arms embargo on the world's newest state and sending more troops there, diplomats said.

After violence in South Sudan's capital Juba earlier this month, U.N. Secretary-General Ban Ki-moon called on the Security Council to fortify the peacekeeping mission. He also urged an arms embargo and sanctions for leaders and commanders blocking implementation of an August peace deal.

"South Sudan remains precariously poised on the brink of an abyss," Ban told a council meeting on peacebuilding in Africa. The mandate for the United Nations mission, known as UNMISS, expires on Sunday, so the United States circulated a brief draft resolution on Thursday, seen by Reuters, to the 15-member council to extend the authorization of the force until Aug. 8. It could be adopted on Friday, diplomats said.

The council's veto-wielding powers - the United States, Russia, China, France and Britain - are already discussing a second, more substantial U.S. draft resolution that would impose an arms embargo and authorize more troops, diplomats said.

Russia and China, who were previously opposed to an arm embargo on the oil producing country, have signaled they are willing to consider such a move.

"We need to look at the situation and what the best way is to be helpful," China's U.N. Ambassador Liu Jieyi told reporters on Thursday.

U.S. Ambassador to the United Nations, Samantha Power, said the council needs a single approach to end the violence in South Sudan.

"In the immediate term this means working with and pressing South Sudan's leadership to provide for security in Juba, to safeguard freedom of movement and to provide for unfettered humanitarian access," she told the council meeting.

She said it also meant answering calls to strengthen UNMISS.

African leaders have called for the Security Council to authorize the deployment of a regional protection force to separate South Sudan's warring parties.

U.N. peacekeepers have been deployed in the country since it gained independence from Sudan in 2011. There are currently some 13,500 troops and police on the ground.

Heavy fighting involving tanks and helicopters raged in Juba for several days between troops loyal to President Salva Kiir and those backing Vice President Riek Machar earlier this month. At least 272 people were killed before the leaders ordered a ceasefire.

Machar left Juba after the fighting and said he would only return after international troops are deployed as a buffer force to separate his forces from Kiir's.

(Reporting by Michelle Nichols; Editing by Tom Brown)