The United Nations said on Thursday it would temporarily evacuate hundreds of its international staff from Afghanistan due to deteriorating security, a sharp blow for Western efforts to stabilize the country.

Spokesman Aleem Siddique said the United Nations would relocate about 600 of its roughly 1,100 international staff, with some being moved to safer sites within Afghanistan and the rest withdrawn from the country temporarily.

The move, a week after five U.N. foreign staff were killed by militants in Kabul, is a blow for U.S. president Barack Obama''s counter-insurgency war strategy, which foresees an influx of civilian assistance alongside extra troops.

Obama is due to decide within weeks whether to approve a request from his commander in Afghanistan for tens of thousands of additional troops. The U.S. force in Afghanistan has already doubled in the nine months since Obama took office.

The United Nations said its evacuation would not disrupt its operations in the country.