NATO Summit first day overshadowed by tensions between allies

Meanwhile, the first day of the NATO summit also saw allies trying to strengthen the defense bloc, with several decisions made related to improved capacity, and even a formal invitation to Macedonia to join as the newest member of the organization.

Praising new initiatives to build capacity, NATO Secretary General Stoltenberg estimated that as much as 266 billion additional U.S. dollars would be spent by European allies and Canada on defense by 2024.

He also announced the agreement of "Readiness Initiative," including the "Four Thirties" to be ready by 2020: 30 mechanized battalions, 30 air squadrons, and 30 combat vessels, ready for use in 30 days or less.

The organization also extended a formal invitation to Macedonia to become the 30th member of NATO, following the recent thaw in relations between the country and its neighbor Greece. Macedonian citizens will first have to ratify an agreement with Greece, which had long blocked NATO membership for the small Balkan country, which would change its name to "Republic of North Macedonia."

The two-day NATO summit will continue in Brussels on Thursday, with meetings between allies and the presidents of Georgia and Ukraine.