Germany's decision to expel the US CIA station chief in Berlin has met with a cool response from Washington, saying any comment would risk US interests.
The United States has refused to break its silence about a spying row, which led a furious Germany to expel the CIA station chief in Berlin, but concern has deepened among lawmakers about damage to relations with Europe's dominant power.
Germany's decision was a stunning show of discord between two such close allies and a signal that Washington has failed to quell anger over revelations about its espionage tactics in Germany, which has been building for more than a year.
But in contrast with the uproar in Berlin, Washington responded coolly, demurring when asked to comment on Germany's shock move, choosing to instead stress the value of its relationship with Berlin.
White House spokesman Josh Earnest said in Texas, where President Barack Obama was on the road, that any "sort of comment on any reported intelligence acts would put at risk US assets, US personnel and United States national security".
He said that the intelligence relationship between the two countries was crucial to the security of both Americans and Germans and that contacts with Berlin on the issue were taking place through diplomatic, intelligence and law enforcement channels.
National Security Council spokeswoman Caitlin Hayden said it was "essential that cooperation continue in all areas" with Germany.
State Department spokeswoman Jen Psaki said that US Secretary of State John Kerry and German Foreign Minister Frank-Walter Steinmeier would likely speak in the coming days.
US officials habitually decline to discuss intelligence issues in public.
But Germany's move elevated the spying row to a political and diplomatic confrontation between the United States, leader of the West, and Europe's most influential power, as both nations work together to confront global crises, including the showdown with Russia over Ukraine.
Transatlantic intelligence cooperation between the United States, Germany and other key European nations is also crucial to detecting and subverting terror plots, as fears rise that Muslim radicals from Syria holding Western passports could be plotting new attacks.
Political pressure on German leader Angela Merkel is intense over the issue, especially after Washington declined to agree to conclude a "no spy" deal with Germany, similar to the ones it has with allies Britain, Australia, Canada and New Zealand.