Paris: France warned Monday that allegations of Washington spying on its European allies were threatening talks on a crucial free trade pact, as US President Barack Obama vowed to respond to Europe's concerns once he had all the facts.
In his first reaction to the growing scandal, Obama promised an answer to European questions about the alleged bugging of EU offices by US security services.
"When we have an answer, we will make sure to provide all the information that our allies want," Obama, on a tour of Africa, said at a press conference in Tanzania.
Obama stopped short of acknowledging any spying by the US, but suggested snooping was widespread.
"In European capitals there are people who are interested, if not in what I had for breakfast, at least what my talking points would be if I am talking to their leaders," Obama said.
French President Francois Hollande earlier demanded answers from Washington about reports that the US National Security Agency (NSA) bugged European offices and embassies.
US officials have sought to downplay the scandal, with Secretary of State John Kerry insisting that information-gathering was "not unusual".
But European sources said anger over the alleged bugging was genuine and warned the scandal could escalate into a "serious" political crisis, just as Washington and the EU are set to begin sensitive talks next week on the biggest free trade deal ever negotiated.
"We cannot accept this kind of behaviour between partners and allies," Hollande told journalists during a visit to the western city of Lorient.
"We ask that this immediately stop," Hollande said. "There can be no negotiations or transactions in all areas until we have obtained these guarantees, for France but also for all of the European Union."
His comments came after Kerry told reporters at a security forum in Brunei that he was looking into the allegations, but also suggested the spying was business as usual.
"I will say that every country in the world that is engaged in international affairs, of national security, undertakes lots of activities to protect its national security and all kinds of information contributes to that," Kerry said.
"All I know is that is not unusual for lots of nations. But beyond that, I'm not going to comment any further until I have all of the facts and find out precisely what the situation is."
In fresh revelations attributed to fugitive leaker Edward Snowden, a former NSA contractor now holed up at Moscow airport, Monday's Guardian newspaper said France, Italy and Greece were among 38 "targets" of spying operations by US intelligence services.
This came after a report in German weekly Der Spiegel detailed alleged covert surveillance by the NSA on EU diplomatic missions.