ATHENS — A former foreign minister of Greece revealed Tuesday that his country’s intelligence services had eavesdropped on the phone conversations of American ambassadors to Greece and Turkey in the 1990s.

Theodoros Pangalos, who was foreign minister from 1996 to 1999, made the comments on Vima FM radio in a discussion about the latest revelations of eavesdropping by the National Security Agency on American allies in Europe. The German newsmagazine Der Spiegel has published a slide purportedly from the N.S.A. showing Athens as one of the locations where the agency had monitoring capabilities.

Mr. Pangalos said that at some time in the late 1990s, Greece’s National Intelligence Service monitored the American ambassadors in Athens and Ankara, the capital of Turkey.

He did not provide a specific time frame for the monitoring, but he said that it did not last long.