The national flag of newly independent South Sudan went up outside the United Nations on Thursday, shortly after becoming the world body's 193rd member.

The U.N. General Assembly in New York admitted the country by acclamation, after a Security Council resolution recommending South Sudan for membership.

The U.S. representative to the U.N., Susan Rice, said South Sudan has taken its rightful place among the community of sovereign nations after great suffering and unimaginable lost.

South Sudan Vice President Riek Machar vowed his country will be a responsible member of the international community and will respect its obligations under international law.

Sudan's U.N. envoy promised Sudan would work with its southern neighbor in a spirit of solidarity, cooperation and coordination for the good of their people.

The world's newest nation declared independence on Saturday, splitting from Sudan. The two sides fought a bloody 21-year civil war that ended in 2005.

The now neighboring countries are still trying to work out disputes over borders and oil revenue. The Ethiopian government says it has started deploying troops to the disputed Abyei region this week. The U.N. Security Council recently authorized deployment of a 4,200 strong-Ethiopian peacekeeping force to monitor the situation there.