JERUSALEM — Syrian rebels control almost all of the villages near the frontier with the Israel-held Golan Heights, the Israeli defense minister said Wednesday, bringing the conflict dangerously close to the Jewish state and raising the possibility of an armed clash with the region’s strongest power.

During a tour of the Golan Heights, Defense Minister Ehud Barak gave a scathing assessment of Syrian President Bashar Assad’s forces and said Israel will remain ‘‘vigilant and alert.’’