Russia is testing NATO’s willingness to respond to provocation ahead of an expected meeting between President Vladimir Putin and his U.S. counterpart Donald Trump, according to Estonian Defense Minister Margus Tsahkna.

Russia’s build-up of forces and violations of international law, including in Ukraine, show the need for members of the North Atlantic Treaty Organization to increase spending on defense, Tsahkna, 39, said in an interview in Brussels on Wednesday, where NATO defense ministers met their new U.S. counterpart James Mattis for the first time.

The 1.3-million-strong Baltic nation is one of just five NATO members whose spending on defense meets the alliance’s target of 2 percent of gross domestic product.

“When we look at Russia’s behavior after the U.S. elections, they have slowly been increasing tensions, and their behavior has become more aggressive, including on violating international law,” Tsahkna said. “The limits are really being tested now. I hope this won’t open new conflict areas. That’s why NATO has to be prepared.”