John Emerson – the American ambassador in Berlin – has been summoned over claims that the US monitored German Chancellor Angela Merkel’s mobile phone.
German Foreign Minister Guido Westerwelle will meet John Emerson later in what is seen as an unusual step between close allies.
Angela Merkel has demanded a “complete explanation” of the claims, which are threatening to overshadow an EU summit.
The German Chancellor discussed the issue with US President Barack Obama on Wednesday.
Barack Obama told Angela Merkel the US was not monitoring her calls and would not in future, the White House said.
However, it left open the question of whether calls had been listened to in the past.
French President Francois Hollande had already called for the issue to be put on the agenda of the summit – where EU leaders are due to discuss Europe’s digital economy, economic recovery and immigration – following reports that millions of French calls had been monitored.
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