WASHINGTON, May 18 (Xinhua) -- U.S. President Donald Trump said Thursday that North Atlantic Treaty Organization (NATO) member states who have not met their financial obligations regarding defense will be "dealt with," and specifically called upon Germany to fulfill its obligation.

Trump made the remarks during his meeting with visiting NATO Secretary General Jens Stoltenberg at the White House.

Listing the countries which have "paid the number that they're supposed to be paying," Trump said that there were some who have not yet paid the amount expected of them.

"We have some that don't -- and, well, they'll be dealt with," the U.S. president said.

NATO's European allies have spent more on defense for a second consecutive year in 2017 but the majority of them still failed to meet the target of spending 2 percent of their gross domestic product on defense.

"We're still waiting on 20 member states to meet their NATO commitments," Trump said.

Trump specifically mentioned Germany, urging it to demonstrate leadership in the alliance by "addressing its longstanding shortfall in defense contributions."

"Germany has not contributed what it should be contributing, and it's a very big beneficiary -- far bigger than the United States," Trump said.

Trump also grumbled about Germany "buying massive amounts of gas from Russia and paying billions and billions of dollars."

Germany is set to continue to fall significantly short of the NATO defense spending target, but German Chancellor Angela Merkel said on Wednesday that Germany's commitment to responsibilities it shoulders as part of the military alliance remained a priority for Berlin.

Noting that all NATO members were increasing their defense budgets, Stoltenberg recognized that NATO needed to invest more in security as "we live in a more unpredictable world."

"On defense spending ... we have to do more," the NATO chief said.

Eight NATO allies will reach the 2 percent benchmark by the end of this year, and 15 are on track to spend 2 percent by 2024, according to a statement released by the White House on Thursday.