Kerry's remarks to NATO's political arm, the North Atlantic Council, came as the alliance is divided over the conflict and concerned about rising civilian casualties but working to minimize NATO's involvement, the Los Angeles Times reported.
Noting that NATO is already planning for contingencies in the 2-year-old war, he said the organization needed to "carefully and collectively consider how NATO is prepared to respond to protect its members from a Syrian threat, including any potential chemical weapons threat."
Britain and France already suspect Syria's leader, Bashar Assad, has used chemical weapons on opposition forces and civilians and have asked the United Nations to investigate.
President Obama has declared that Syria's use of such banned weaponry would be a "game changer" and prompt a response from the United States.
Syria is reported to have the third largest stockpile of chemical weapons in the world.
In a statement issued by the State Department after the meeting, Kerry said that while no specific role for NATO was discussed, "we did underscore that the mass murder that is taking place outside of Damascus is unacceptable."