川普周二晚些时候前往比利时，参加北约峰会

U.S. President Donald Trump is continuing to criticize NATO member nations as he prepares to leave Washington for an alliance summit this week in Belgium.

On Twitter Tuesday morning, he said "The U.S. is spending many times more than any other country in order to protect them. Not fair to the U.S. taxpayer. On top of that we lose $151 Billion on Trade with the European Union. Charge us big Tariffs (& Barriers)!"

Trump has been a harsh critic of NATO since he began campaigning to be the U.S. president. Since taking office in 2017, Trump affirmed the U.S. commitment to the defense of NATO allies, but he has continued to criticize NATO's funding, arguing that Washington is shouldering too much of the financial burden.

During a rally last week in Montana, Trump vowed that he would “tell NATO: ‘You've got to start paying your bills.'” The president also said that Americans were “the schmucks that are paying for the whole thing.''

NATO says the United States funded about 70 percent of its expenses in 2017.

NATO's 29 members contribute funds to the organization according to the size of their economies. Member nations committed in 2006 to spend 2 percent of their gross domestic product on defense by 2024, but NATO estimates that not all members will meet the target.

The upcoming NATO summit on Wednesday and Thursday is the first major summit since the fractious Group of Seven meeting in Canada last month. At the conclusion of that meeting, Trump retracted his endorsement of the group's final joint statement and blasted Canadian Prime Minister Justin Trudeau as "very dishonest and weak."

After meeting with NATO leaders in Brussels, Trump travels to Britain where he will meet with Prime Minister Theresa May and Queen Elizabeth II. Trump meets Russian President Vladimir Putin in Helsinki on July 16 the final stop of his European trip.