File photos of US President Donald Trump (L) and British Prime Minister Theresa May.

WASHINGTON - US President Donald Trump is "100 percent" behind NATO, British Prime Minister Theresa May said Friday as she paid a visit to the United States.

"On defense and security cooperation, we are united in our recognition of NATO as the bulwark of our collective defense, and today we've reaffirmed our unshakable commitment to this alliance," May said at a joint press conference following a meeting with Trump.

"Mr. President, I think you said, you confirmed that you're 100 percent behind NATO," she added.

In a recent interview, Trump said NATO was "obsolete because it was not taking care of terror," and he complained that various members of the bloc were not paying their dues, which was "very unfair to the United States."

However, Trump added that NATO was very important to him.

May is the first foreign leader to hold face-to-face talks with Trump after he was inaugurated a week as the new U.S. President.

At the press conference on Friday, May said she will ensure that other European leaders follow through on their commitments to NATO.

"We're also discussing the importance of NATO continuing to ensure it is as equipped to fight terrorism and cyber warfare as it is to fight more conventional forms of war," May said.

The British leader added that she will also continue to encourage other European leaders to deliver on their commitments to spend 2 percent of their country's GDP on defense "so that the burden is more fairly shared."