Germany's intelligence agency has reacted to the continuing row over US spying by commissioning an investigation to unmask further moles in its own ranks.
Gerhard Schindler, president of the agency known as BND, told the government that he had ordered an analysis of his agency's communications for irregularities, according to Der Spiegel.
Similar searches had previously concentrated on identifying Russian and Chinese spies, the magazine said.
The discovery in recent weeks of two suspected US spies on the German government's payroll triggered an official request on Thursday for the CIA's station chief to leave the country.
The move met with cross-party approval in Germany last week. The foreign minister, Frank-Walter Steinmeier, described the request, which does not amount to a formal expulsion, as a necessary response to the US "breach of trust".
Steinmeier confirmed he would meet the US secretary of state, John Kerry, during the Iranian nuclear talks in Vienna this week. He said he hoped the meeting would lead to a new start for the US and Germany. "It would be an illusion to assume conflicts can be defused and political solutions can be worked out without closely collaborating with the US," he said.
A recent survey by Germany's TNS research institute illustrated what a devastating impact the string of spying allegations over the past year has had on the German public's view of the United States. Of those surveyed, 69 per cent told researchers their trust in the US had shrunk, while 57 per cent called for more independence from the US. As many as 40 per cent said they would approve of closer collaboration between Germany and Russia.
It remains unclear whether US intelligence services were pursuing a specific goal in their correspondence with contacts within the German authorities. Originally, there was speculation that US spy agencies may have been trying to obtain information about the government's parliamentary investigation into NSA surveillance in Germany.
Members of the legisalture's supervisory panel said on Thursday that they believed that motive was unlikely.
Out of the cache of 215 confidential documents the BND staffer is alleged to have sold to contacts at the CIA for €25,000 (HK$264,000), only one is said to concern the activities of the NSA committee.