BRUSSELS -- U.S. General Curtis Scaparrotti, NATO's supreme allied commander in Europe, has warned that the alliance will not be “dominant” in certain areas in five years if it fails to modernize and adapt to the growing threat from Russia.

“I certainly have concerns with respect to Russia,” Scaparrotti told a press conference in Brussels on January 17 following a meeting of top NATO defense officials.

“I think that, as an alliance, we are dominant. There are domains within this that were challenged. I think cyber is one of those. They are very competent in that,” he also said, referring to Russia.

“There are others where because of the modernization you noted, while we are dominant, we will not be in five years per se if we aren't adapting like this to include our structure but also within the nations, our capabilities, across the military functional areas as well as our domains.”

Addressing the session of the Military Committee, the alliance’s highest military authority, Scaparrotti said earlier that “a resurgence of Russia as a strategic competitor, growing unrest and instability in Africa and the Middle East, as well as terrorism, [are] reshaping our strategic environment.”

Relations between Moscow and the West have been severely strained over issues including Russia's seizure of Ukraine's Crimea region in March 2014 and its support for separatists who control parts of eastern Ukraine.

The war between Kyiv's forces and the Russia-backed separatists has killed more than 10,300 people since April 2014.

Amid growing tensions, NATO stepped up its defenses in Eastern member nations near Russia.

Speaking alongside Scaparrotti at the press conference, Czech General Petr Pavel, chairman of the Military Committee, called Russia an “obvious security challenge.”

“We characterize Russia as a peer competitor and we obviously follow closely all the development and modernization and taking all the measures that are necessary to be ready for any contingency,” he added.

Ahead of the meeting, NATO said the top defense officials would discuss “the challenging security environment on NATO’s southern flank and the alliance’s contribution to its stabilization” and would review NATO’s Resolute Support Mission in Afghanistan and the international coalition against the extremist group Islamic State.

They also held separate talks with top defense officials from Ukraine and Georgia on “the security situations on the ground, defense reform progress, and the way ahead.”

After the meetings, Pavel told reporters that the defense officials “noted the challenge for Ukraine of achieving security and defense reforms alongside reestablishing Ukraine's territorial integrity.”

They also “stressed their commitment on furthering the capability and interoperability of the Ukrainian armed forces,” he added.

On Georgia, Pavel said the defense officials “stressed continued support” to the Substantial NATO-Georgia Package to enhance the country’s defense readiness.

