KABUL, Dec. 11 (Xinhua) -- On a surprise visit to Afghanistan Thursday, U.S. Defense Secretary Robert Gates said Pentagon would pledge three more combat brigades to the strife-torn country by the summer of 2009.

    Gates flew to the riot southern Afghan province of Kandahar and would meet with military leaders from both the U.S.-led Coalition forces and the NATO-led International Security Assistance Force (ISAF), said officials from the Pentagon's office.

    The Defense Secretary told newsmen traveling with him aboard the plane that Pentagon is moving to get three of the four combat brigades requested by commanders into Afghanistan by next summer, adding that "we will not have to cut troop levels further in Iraq to free up at least two of those three brigades for Afghan duty."

    Gates, as the top gunman for U.S. president-elect Barack Obama, said in November that Washington wanted to send additional 20,000 troops to Afghanistan among which 3,500-strong soldiers of one brigade will be deployed in the capital city of Kabul next January for enhancing security of the coming Afghan presidential election.

    More than 30,000 U.S. troops have been deployed in post-Taliban Afghanistan fighting against militant activities and helping with reconstruction.