Will Trump extort a price from NATO?

US President Donald Trump warned other NATO leaders the United States would alter the military deployment in European countries if they didn't increase their defense budgets, raising worries that the NATO summit in Brussels on Wednesday and Thursday could end like the G7 summit in Canada last month - in disorder.

The US has been exhorting other NATO member states to raise their defense budgets. In 2014, they inked an agreement that said 15 countries, or half of the NATO members, would spend at least 2 percent of their GDP on defense until 2024. According to latest data of NATO, in 2016 the US spent about $603 billion on defense, accounting for 3.56 percent of its GDP, with the defense budgets of the other 27 NATO members adding up to about $286 billion.

"By some accounts, the U.S. is paying for 90 percent of NATO, with many countries nowhere close to their 2 percent commitment ... On top of this the European Union has a Trade Surplus of $151 Million with the U.S., with big Trade Barriers on U.S. goods. NO!" Trump tweeted on Monday.