Washington, June 28 (IANS) The US has welcomed swift passage of a UN Security Council resolution authorising deployment of 4,200 Ethiopian peacekeepers to the volatile Abyei region of Sudan.

The US, however, has expressed deep concern about the ongoing crisis in neighbouring South Kordofan state.

"Abyei has been a source of regional tension for many years, as the world witnessed last month when Sudanese armed forces forcibly took control of the region, resulting in widespread displacement and looting," US Secretary of State Hillary Clinton said in a statement.

Clinton called the UN Security Council's move "a critical step" in implementing the June 20 agreement signed by the parties in Sudan, whereby the Sudanese armed forces will withdraw from the Abyei region along with southern Sudan People's Liberation Army forces there.

The oil-rich Abyei region is claimed by both -- north and south Sudan. The northern Sudanese Armed Forces occupied Abyei on May 21, leading to more than 100,000 people fleeing their homes, mainly to the south. The two sides agreed on June 20 to demilitarise the area.