The case of a German intelligence operative suspected of spying for Washington drew a fierce response from Berlin, where indignation against one of its closest allies has run high since reports last year that the US National Security Agency (NSA) tapped Chancellor Angela Merkel's mobile phone.
Merkel fumed over the latest allegations on a visit to China, saying on Monday that if they proved to be true it "would be for me a clear contradiction as to what I consider to be trusting cooperation between agencies and partners."
Members of her cabinet went further, with Justice Minister Heiko Maas saying that German authorities should consider "criminal proceedings" against US spies.
"The American intelligence services are obsessed with surveillance," he said.
NATO partners including Washington are currently exempt from targeted German espionage operations under orders from Merkel's office, the daily Bild reported.
The deputy head of Merkel's Christian Democrats parliamentary group, Andreas Schockenhoff, demanded a formal expansion of the BND foreign intelligence service's remit to include the United States.
"We must not be blind in one eye," he told the daily Stuttgarter Nachrichten.
Katrin Goering-Eckardt of the opposition Greens renewed a call to bring fugitive US leaker Edward Snowden, whose revelations touched off the NSA affair one year ago, to Germany to be questioned.
"You don't get respect by shutting your mouth in shame but rather when you bring Edward Snowden to Germany as a witness, give him a safe haven and get information that cannot be obtained otherwise," she told the Passauer Neue Presse newspaper.
Berlin has declined to invite Snowden to testify, citing the potential damage to US relations.
Some called for cooler heads to prevail, saying the country's spies had little chance of beating the Americans at their own game and calling for Germany to respect the lessons of its history of mass state snooping under the Nazi and communist regimes.
"You cannot criticise the massive collection of data by US agencies and then do the same," Rolf Muetzenich, deputy head of the parliamentary group of the Social Democrats, partners in Merkel's left-right government, told the Stuttgarter Nachrichten.
Restraint vs. revenge
After a long weekend of silence on the alleged German mole, the White House Monday declined to comment on the case but pledged to work with Berlin "to resolve this situation appropriately".
"The relationship that the US has with Germany is incredibly important," spokesman Josh Ernest said.
A German government spokeswoman, Christiane Wirtz, said only that Berlin would "have to wait and see what consequences there will be" for transatlantic ties.
But she insisted that the latest flap would have "no bearing" on negotiations for an ambitious transatlantic trade pact known as TTIP, which Merkel has named as a key foreign policy goal.
Some documents allegedly passed by the suspect to the CIA included information on a committee of German lawmakers probing Snowden's allegations.
Henning Riecke, an expert in transatlantic relations at the German Council on Foreign Relations, said this violation, if proven, was on a par with snooping on Merkel's phone and was extremely short-sighted.
"This has nothing to do with counter-terrorism or homeland security -- this is purely about agencies protecting themselves," he said.
Riecke said Germany's room for manoeuvre against the US was limited given the long list of shared concerns in countries such as Afghanistan, Ukraine and Iran.
He said it should reach out to like-minded members of the US Congress with an interest in reining in the secret services, boost its espionage defences and bolster its own intelligence gathering to improve its negotiating position with Americans.
"Revenge isn't the answer," he said.
Skilled operative or dabbler?
Meanwhile, the lawyer of the arrested BND worker has said that there was some truth to the swell of media reports about his client, who reportedly sold 218 documents over two years for €25,000 to US secret services.
“He still needs questioning, but there are things in the media which are true,” Klaus Schroth told broadcaster SWRinfo.
Schroth, who said he first met the man in Karlsruhe at the Attorney General’s office, was skeptical after media portrayals of his client as a skilled operative.
“I have worked on lots of espionage cases but my client doesn’t give me the impression that he is a professional spy," he added.
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