Mattis praised Estonia for dedicating two percent of its GDP to defense spending. He also reaffirmed that the U.S. is dedicated to the defense of the Baltic states, especially from the threat of Russia, reported ERR's radio news.

"Russia is trying to change international borders by force and achieve veto rights in European countries' diplomatic, economic and security decisions, and as NATO Secretary General [Jens] Stoltenberg said last Monday, NATO does not want a new Cold War, but we will respond, as we are seeing a more robust Russia," Mattis said.

The two defense ministers likewise discussed the upcoming NATO summit in Brussels, one of the key topics of which will be the the high readiness of allied forces.

"It's one thing for some unit to be assembled over the course of a month," Luik explained. "This may no longer be of any help, and the U.S. has actually proposed a high readiness initiative, which we also very much support, which would increase the number of units that can be deployed rapidly for the execution of NATO tasks."

Mattis also thanked Estonia for joining other NATO member states in deciding to send additional troops to Afghanistan; a total of 40 personnel will be headed there from Estonia.

"This is all based on the U.S. NATO strategy that a somewhat larger military contingent will be better able to advice Afghan fighters, and Afghan security organizations," said Luik. "Peace will naturally ultimately be achieved in Afghanistan when the Afghans themselves are able to make it happen, but we will try to help them as much as possible."

The two officials also discussed at length Estonian-U.S. cyber cooperation.

Luik is scheduled to meet with President Donald Trump's National Security Advisor H. R. McMaster on Thursday.