The United States is urging the United Nations to sanction individuals in South Sudan who are accused of blocking peace in the world's newest country.

Donald Booth, the U.S. envoy to South Sudan and Sudan, did not say who should be targeted. But he said South Sudan's leaders squandered an opportunity for peace and prosperity when the country broke away in 2011.

Booth said in a speech on Thursday in Washington that the U.N. Security Council should decide what sanctions to impose, but did not rule out an arms embargo.

The U.S. has been trying to help broker a cease fire in South Sudan, where forces loyal to President Salva Kiir and his rival, former Vice President Riek Machar, have been fighting for power for nearly a year.