"Tremendous progress has been made and NATO's much stronger," Trump told reporters as he met NATO chief Jens Stoltenberg ahead of the alliance's 70th anniversary celebrations in Washington.

"It's a rocket ship up," he said of the spending. "People are paying and I'm very happy."

Trump has long voiced skepticism about NATO, accusing Western allies of being freeloaders that do not pull their weight on military spending.

The Trump administration has been especially incensed with Germany, Europe's largest economy, which is not on track to meet a 2014 pledge by NATO members to spend two percent of GDP on defense.

Stoltenberg, a former Norwegian prime minister, has stood behind Trump on the spending goals and credited his blunt approach with pushing members.

Between 2016 and the end of next year, the 28 NATO members other than the United States will have boosted military spending by $100 billion, Stoltenberg said earlier this year.

Trump said that he was also looking for a better relationship with Russia -- now, as 70 years ago, seen as the primary threat by the Western alliance.

"I hope we have a good relationship with Russia," Trump said. "I think we'll get along with Russia."

The comments come little more than a week after a long-awaited probe by former FBI chief Robert Mueller found no criminal collusion between Trump's 2016 presidential campaign and Russia, according to a synopsis released by the Justice Department.