Security in Afghanistan has "deteriorated markedly" in the past six months, United Nations Secretary-General Ban Ki-moon said in a report that cited 983 armed clashes in August, the highest number since the fall of the Taliban regime in 2001.

"The influence of the insurgency has expanded beyond traditionally volatile areas and has increased in provinces neighboring Kabul," Ban said in a report to the UN Security Council. "`We are at a critical juncture in our efforts in Afghanistan."

Ban said there were 1,445 civilian deaths in the first eight months of 2008, an increase of 39 percent over the same period last year. Of those, 393 resulted from U.S. and allied air strikes and 794 from anti-government forces led by the Taliban.

The U.S.-led war to stabilize Afghanistan has become a major issue in the presidential campaign between Democratic nominee Barack Obama and his Republican opponent, John McCain. Both have pledged to send more U.S. troops to Afghanistan in an effort to defeat the Taliban and al-Qaeda terrorists.