PARIS — French President Emmanuel Macron on Monday declared that wiretapping "is not acceptable between allies" and asked the United States for clarity after new claims emerged about National Security Agency efforts to spy on European leaders between 2012 and 2014.

Denmark’s public broadcaster reported over the weekend that the Danish foreign intelligence service had helped the NSA gain access to underwater Internet cables, allowing officials to track calls, messages, chats and browsing histories of select targets in an operation code-named Dunhammer.

The NSA’s wiretapping of friendly foreign leaders, including German Chancellor Angela Merkel, was first revealed in documents leaked by former contractor Edward Snowden in 2013. According to the latest reports, the Danish agency also helped the NSA to monitor officials and high-profile politicians in France, Norway and Sweden.

The practice, current and former U.S. officials say, should not come as a surprise, because allies routinely spy on each other.

A spokeswoman for the National Security Council declined to comment on Monday. A spokesman for the NSA also declined to comment.

“There is no room for suspicion between” the United States and its European allies, Macron said Monday, speaking after a Franco-German video summit. “We requested that our Danish and American partners provide all the information on these revelations and on these past facts. We are awaiting these answers,” he added.

Merkel said she “could only agree” with Macron.

In 2013, the revelations shook political relations between the United States and Europe. “Trust needs to be rebuilt,” Merkel said at the time. Intelligence sharing among allies and partners, though, continued.

James R. Clapper Jr., who was director of national intelligence at the time, recalled the diplomatic tensions after the Snowden leak, which included reports that the NSA had collected millions of digital communications in France and the phone calls of the Brazilian and Mexican presidents.

“We had many uncomfortable and awkward meetings,” Clapper said. “We had our usual venting sessions and went on with business. We acknowledged that nation-states do things in their interest.”

In a 2014 speech, President Barack Obama promised that the United States would not track the communications of “heads of state and government of our close friends and allies” — “unless there is a compelling national security purpose.” That gives intelligence agencies plenty of wiggle room.

Espionage can be a stabilizing factor, intelligence experts say, reducing the chances of surprise.

“I think nations would be irresponsible if they didn’t conduct some sort of spying operations, even on their supposed allies,” Robert Deitz, a former NSA general counsel and a former senior counselor to ex-CIA director Michael V. Hayden. “Even close allies that have enormous trust in each other’s governments reserve the right to spy on the citizens of those countries for their own national security.”

Added Deitz, a professor of public policy at George Mason University: “Even our European friends are known to spy on us from time to time.”

In 2015, Germany’s Süddeutsche Zeitung reported that the German foreign intelligence service, the Bundesnachrichtendienst, had aided U.S. agents with monitoring politicians, companies and others in several neighboring countries, including France.

Nakashima reported from Washington.