BERLIN — The United States could lose access to an important law enforcement tool used to track terrorist money flows, German officials said Monday, as Europe weighs a response to allegations that the Americans spied on their closest European allies.

Spain became the latest U.S. ally to demand answers after a Spanish newspaper reported that the National Security Agency monitored more than 60 million phone calls in that country during one month alone. The report Monday in the daily El Mundo came on the heels of allegations of massive NSA spying in France and Germany, including Chancellor Angela Merkel’s own cellphone.

With European leaders dissatisfied with the U.S. response so far, officials have been casting about for a way to pressure Washington to provide details of past surveillance and assurances that the practice will be curbed. The challenge is to send a strong message to Washington against wholesale spying on European citizens and institutions without further damage to the overall trans-Atlantic relationship.

As possible leverage, German authorities cited last week’s non-binding resolution by the European Parliament to suspend a post-9/11 agreement allowing the Americans access to bank transfer data to track the flow of terrorist money.

German Justice Minister Sabine Leutheusser-Schnarrenberger said Monday she believed the Americans were using the information to gather economic intelligence apart from terrorism and that the deal, popularly known as the SWIFT agreement, should be suspended. That would represent a sharp rebuke to the United States from some of its closest partners.

“It really isn’t enough to be outraged,” she told rbb-Inforadio. “This would be a signal that something can happen and make clear to the Americans that the (EU’s) policy is changing.”

Suspending the agreement, officially known as the Terrorist Finance Tracking Program, would require approval by an overwhelming majority of the 28 European Union countries. The agreement allows access to funds transferred through the private, Belgium-based Society for Worldwide Interbank Financial Telecommunication, which handles the movement of money between banks worldwide.

Asked Monday if the NSA intelligence gathering had been used not only to protect national security but American economic interests as well, White House spokesman Jay Carney said: “We do not use our intelligence capabilities for that purpose. We use it for security purposes.”

Still, he acknowledged the tensions with allies over the eavesdropping disclosures and said the White House was “working to allay those concerns,” though he refused to discuss any specific reports or provide details of internal White House discussions.

The German justice minister’s comments follow days of vocal indignation in Berlin after German news weekly Der Spiegel reported the NSA had kept tabs on Merkel’s phone calls since as early as 2002, three years before she became chancellor.

Merkel said Friday that she was open to the idea of suspending the SWIFT agreement, saying she “needed to look at this again more closely” and weigh “what we will lose for the security of our citizens and what we don’t.”

Germany and other European governments have made clear they don’t favor suspending the U.S.-EU trade talks which began last summer because both sides stand to gain so much through the proposed deal, especially against competition from China and other emerging markets.

Still, the Europeans have said they will insist that the trade agreement includes stronger rules for protecting data as a result of the NSA allegations. Data-protection laws in Europe are generally stronger than in the United States.

“It’s obvious to us that we have to and will bring our European convictions regarding data protection, and protection of privacy and business information, into these negotiations,” Merkel’s spokesman Steffen Seibert told reporters in Berlin on Monday.

The European Parliament’s foreign affairs committee chairman, Elmar Brok, told reporters that failure to resolve the differences over data protection could threaten the trade talks. Brok, a member of Merkel’s party who was in Washington to discuss the spy allegations, said the challenge was to strike a balance between security and personal freedom.

“We are fighting for the rights of our citizens,” he said.