US President Barack Obama was dragged further into the trans-Atlantic spying row after it was claimed he personally authorised the monitoring of Angela Merkel's telephone three years ago.
Scrambling to contain the growing diplomatic fallout, the National Security Agency (NSA) was forced last night to deny reports that Mr Obama allegedly allowed US intelligence to listen to calls from the German Chancellor's mobile telephone after he was briefed on the operation by Keith Alexander, director of the NSA, in 2010.
The latest claim, reported in the German newspaper 'Bild am Sonntag', followed reports in 'Der Spiegel' that the surveillance of Mrs Merkel's telephone began as long ago as 2002 when she was still the opposition leader, and three years before being elected chancellor. That monitoring only ended in the weeks before Mr Obama visited Berlin in June this year, the magazine added.
Citing leaked US intelligence documents, it also reported that America conducted eavesdropping operations on the German government from a listening post at its embassy beside the Brandenburg Gate in Berlin, one of more than 80 such centres worldwide.
Mr Obama's European allies will now ask him to say what he personally knew about the NSA's global eavesdropping operation and its targeting of world leaders, including those from friendly states. The White House declined to comment on the German media reports.
However, an NSA spokesman said Mr Alexander "did not discuss with President Obama in 2010 an alleged foreign intelligence operation involving German Chancellor Merkel, nor has he ever discussed alleged operations involving Chancellor Merkel".
Last week, Mr Obama assured Mrs Merkel her phone is not being monitored now and will not be in future. But the US has refused to discuss the NSA's actions in the past. Its surveillance operations raise questions about whether US officials breached domestic laws.
German Interior Minister Hans-Peter Friedrich said: "If the Americans intercepted cellphones in Germany, they broke German law on German soil."
He noted that wiretapping was a crime in Germany and "those responsible must be held accountable".
Even before the latest reports, German intelligence chiefs were preparing to travel to Washington this week to demand answers from the NSA about the alleged surveillance of Mrs Merkel.
John Kerry, the US secretary of state, received a dose of European fury this weekend when he visited Paris and Rome to discuss the Middle East. He was confronted by outrage over the scale of US surveillance operations.
"The magnitude of the eavesdropping shocked us," said Bernard Kouchner, a former French foreign minister, in a radio interview.
According to the leaked documents in 'Der Spiegel', NSA officials acknowledged that disclosure of the existence of the foreign listening posts would lead to "grave damage" for relations with other governments. Such posts exist in 19 European cities, including Paris, Madrid, Rome and Frankfurt, according to the magazine, which has based its reports on documents provided by Edward Snowden, the former NSA contractor.
Mr Obama did not comment, but Republican supporters of the US intelligence community began a fightback on talkshows.
"If the French citizens knew exactly what that was about, they would be applauding and popping champagne corks," he told CNN's State of the Union. "It's a good thing. it keeps the French safe. It keeps the US safe."
John Schindler, a former NSA official, said planning for September 11, 2001, had taken place in Hamburg. "If 9/11 had happened to Germany and been planned in NY, not Hamburg, I'd expect (German) intel to monitor USA top 2 bottom," he wrote on Twitter. (© Daily Telegraph, London)
Philip Sherwell in New York and Louise Barnett in Berlin