Turkey's foreign ministry on Monday summoned the U.S. embassy undersecretary and called for an end to a dispute between the two countries, Turkish foreign ministry sources said, after the NATO allies suspended visa services.

The sources said the undersecretary was told the visa suspension move caused "unnecessary tensions" and should be reversed. They said Turkey's foreign ministry undersecretary also spoke by phone with the U.S. ambassador on Sunday.

In a move signalling a sharp deterioration in relations between the two NATO allies, the U.S. mission in Turkey and the Turkish mission in Washington mutually scaled back visa services after a U.S. consulate employee was arrested in Turkey.