A U.N. peacekeeper stands guard at an outpost outside the United Nations Mission in South Sudan compound in Malakal, South Sudan, in July. (Jane Hahn/For The Washington Post)

THE LATEST round of bloodshed in South Sudan has, at long last, prompted the United Nations to step up its efforts to help bring peace to the troubled nation. On Friday, the United Nations Security Council voted to enhance and extend the mandate of the United Nations Mission in South Sudan and to increase the number of troops on the ground by 4,000. We aren’t convinced that more peacekeepers will be very effective — considering that the existing 12,000-strong U.N. force has failed to protect civilians thus far. But the mandate is certainly an improvement to the U.N. operation , notably in that the added troops will be deployed as a special protection unit with the power to engage any actor committing violence against civilians, including government forces.

After initially vowing to reject the force, South Sudan has said that it will consider accepting the expanded force, if it can negotiate on the size, mandate and contributing countries. This reversal comes after a fresh outbreak of violence on Saturday between forces supporting President Salva Kiir and his former deputy, Riek Machar. Should South Sudan refuse to allow troops, the U.N. is prepared to impose an arms embargo. While an incomplete solution, an arms embargo would at least help to reduce the amount of suffering inflicted on South Sudanese civilians. The White House has long been reluctant to impose an arms embargo, hoping the threat of one would be enough to coerce the warring leaders to pursue peace. Clearly that strategy has not worked. Should the government of South Sudan reject or impede the latest U.N. resolution, an arms embargo should be implemented without delay, and the United States should get on board.

Two years ago, Mr. Kiir and Mr. Machar, leaders of the young nation, plunged it into an unneccesary civil war. They promised last year, under pressure from President Obama, to make peace, but have since undercut the deal. Mr. Kiir’s allies have not only battled Mr. Machar’s forces in the streets, but also committed horrendous abuses during fighting, including rape and other crimes. In a politically reckless move, Mr. Kiir elected to remove Mr. Machar as vice president, and Mr. Machar disappeared after clashes in July. His party replaced him with the mining minister, Taban Deng Gai, as vice president. Mr. Kiir fired a number of allies loyal to Mr. Machar. The South Sudanese government says that while Mr. Machar was signatory to the peace agreement, he is not needed to implement the accord. However, as long as his whereabouts and intentions remain unknown, he is a wild card in a volatile situation.

The United Nations’ resolution is a welcome sign of renewed efforts on the part of the international community to halt South’s Sudan’s downward spiral. Mr. Kiir and Mr. Machar have spent years and millions in international funds jetting from African capital to capital, claiming to respect the peace agreement while they are abroad, yet engaging in war and human rights abuses at home. It is long past time for Mr. Kiir to get on with the business of building South Sudan for its hungry, displaced, sick and suffering population. Accepting the new U.N. force is a needed first step.