UPDATE 1-Security Council recommends S.Sudan as UN member

* General Assembly set to admit South Sudan Thursday

* U.S. accuses Khartoum forces of killing civilians (Adds quotes, background)

By Patrick Worsnip

UNITED NATIONS, July 13 (Reuters) - The Security Council formally recommended on Wednesday that newly independent South Sudan be admitted as a member of the United Nations.

Following the recommendation, in a five-line resolution adopted without a vote by the 15-nation council, the General Assembly is expected to admit the new African country as its 193rd U.N. member on Thursday.

South Sudan achieved independence on Saturday after its people voted for secession from the rest of the country in a January referendum, under the terms of a 2005 peace deal that ended a 20-year war between north and south Sudan.

Sudan became independent in 1956 but was long plagued by conflict between its mainly Muslim Arabic-speaking north and its black African south, where many are Christian or follow traditional beliefs.

U.N. membership is the gold standard of statehood and a goal aspired to by separatist movements around the world. The last country to achieve it was Montenegro in 2006 but veto-holding China and Russia have blocked Taiwan and Kosovo respectively from joining the world body.

Since Khartoum's acceptance of South Sudan's independence in February, Juba's U.N. application has been uncontested and a committee charged by the Security Council on Monday with studying it reported back favorably in less than 48 hours.