U.S. Secretary of Defense Donald Rumsfeld has made a surprise visit to South Korean troops stationed in the northern Iraqi region of Irbil.

After arriving at the Irbil airport aboard a helicopter Sunday, Rumsfeld met with some 500 soldiers of the Zaitun unit and expressed Washington's gratitude for Seoul's contribution to U.S.-led efforts to rebuild the war-torn country and fight international terrorism.

Rumsfeld conveyed words of encouragement to the South Korean troops, saying the soldiers' courage, hopeful example and skills would greatly help the people of the war-devastated nation. He stressed that the half-century-old South Korea-U.S. alliance is both significant and special.

Sunday's visit was Rumsfeld's first to non-U.S. foreign forces stationed in Iraq.

Following his visit, Rumsfeld telephoned South Korean Defense Minister, Yoon Kwang-ung, and again thanked Seoul for its troop contribution.

Approximately 2,800 South Korean troops were dispatched to the Kurdish-controlled city in late September for reconstruction work.

South Korea maintains the second-largest military presence after Britain in the U.S.-led coalition forces in Iraq.