Gen. Joseph Dunford's visit today marks the first time a sitting Joint Chiefs of Staff chairman has ever spoken at the world body, US officials said.
Deputy British chief of Defense Staff Gen. Gordon Messenger is a co-host of the meeting.
The meeting seeks to provide an update on pledges made at President Barack Obama's 2015 Leaders' Summit on Peacekeeping, where countries promised nearly 50,000 troops for UN missions.
The officials declined to be identified because they spoke at a background briefing ahead of the closed meeting.