KABUL, Dec. 22 (Xinhua) -- U.S. Vice President Mike Pence paid a pre-Christmas visit to American troops in Afghanistan, sources said on Friday.

The visiting U.S. vice president met with Afghan President Ashraf Ghani and discussed various topics Thursday night, the source told Xinhua.

They had a productive meeting to reaffirm the enduring strategic partnership between Kabul and Washington and discussed security in Afghanistan and in the region, he said.

Foreign dignitaries usually pay unannounced visit to militancy-hit Afghanistan and return to their home countries secretly due to security concerns.