The United Nations said on Tuesday it had temporarily withdrawn foreign staff and shut its mission in Kandahar, the Afghan city where security has deteriorated ahead of a major military offensive. UN spokeswoman Susan Manuel said some foreign staff in the Kandahar office had been moved to the capital Kabul for their safety, and Afghan staff there had been told to stay home. She would not say how many international staff had been withdrawn and how many had stayed behind or whether a specific threat was behind the decision. “The security situation has gotten to the point where we needed to withdraw them yesterday,” she said. “We hope people can go back and keep doing what they have been doing. We see it as a very temporary measure.” NATO forces are planning the biggest military offensive of the nearly nine-year-old war in coming months in and around Kandahar, the biggest city in the south and heartland of the Taliban movement. Under the plans, expected to unfold beginning in June, about 8,000 US and Canadian troops will secure rural areas around the city while a newly-deployed brigade of 3,500 US troops escorts 6,700 Afghan police into urban areas. In all, the offensive will involve some 23,000 NATO ground troops and Afghan police. The offensive is the cornerstone of a “surge” strategy by US President Barack Obama, employing the bulk of the 30,000 extra troops he is dispatching to Afghanistan this year to turn the tide against a mounting Taliban insurgency.