President Trump kicked off the summit of NATO allies in Brussels Wednesday morning by calling out countries for not paying as much as the United States when it comes to defense spending. Mr. Trump also claimed Germany's oil and gas imports leave it "totally controlled" by Russia.

Ian Bremmer, the founder and president of Eurasia Group, says President Trump's approach is something more in line with what China usually does.

"He doesn't like any of these multilateral meetings," Bremmer said. "He feels like they're opportunities for the allies to gang up on the Americans. America's weaker. He takes a Chinese approach. He wants a one-on-one meeting where he's stronger and he wants to link security to economics, just like the Chinese do. They'll give you money if you play ball with them politically on a security perspective. It's the same thing Trump is doing."

Bremmer says Mr. Trump has been consistent with that style of negotiation throughout his presidency.

"'South Korea, you want me to defend you? You better give me what I want in a deal.' 'Europeans, you want me to complain or do something right on NATO? Deal with trade,'" Bremmer said. "It's linkage and it's really not been the American approach, it's been the Beijing approach."

But Bremmer says Mr. Trump's hard stances have yet to have an impact on NATO negotiations, aside from making allies uncomfortable. He has yet to offer up a plan for what happens if NATO countries don't raise defense spending to 2 percent of their GDP by 2024, a goal they set in 2014.

"There's no, 'or else,' he hasn't said what he's going to actually do if they continue to underpay," Bremmer said. "And the Germans are not going to come close to the 2 percent commitment by 2024. They're good on all sorts of other commitments, social spending, for example. They're good on their climate commitments, but for some reason, not on defense.

"So the fact that Merkel and Trump really can't stand each other and that this is really the part of the transatlantic partnership that's most rubbing against each other, was on obvious display with the G7, it's on obvious display as NATO opens. But so far, no direct impact on NATO itself."