BRUSSELS - Top NATO brass are meeting behind closed doors to discuss what changes the alliance should make in its strategy and force posture to face a more assertive Russia and other evolving security challenges.

Gen. Petr Pavel, chairman of NATO's Military Committee, said Thursday's meeting in Brussels is intended to generate advice to member governments in the run-up to the NATO summit in July in Warsaw.

"The most important task for us, the military leaders and advisers to our heads of state and government, is to steer a clear course through these rough seas," Pavel said in brief public remarks before the meeting went into closed session.

Marine Gen. Joseph Dunford was attending for the first time as chairman of the U.S. Joint Chiefs of Staff.