The fugitive Snowden was granted asylum in Russia last year after exposing details of massive U.S. intelligence-gathering programs at home and abroad. It is considered unlikely that he would set foot in any U.S.-allied country like Germany because of the risk of being arrested and extradited.

But in a report, the German government made clear it had no wish to see Snowden come to testify in parliament as this "would have a significant negative impact on the German-American relationship, particularly on cooperation with U.S. intelligence".