Western diplomats in Paris said a top general's flight from Syria is a sign of how regime elites are abandoning President Bashar al-Assad, heralding the defection during an international summit on Syria that otherwise highlighted the international deadlock over the conflict.

Brig. Gen. Manaf Tlass, whose defection was reported Thursday, was on his way to Paris on Friday, according to French Foreign Minister Laurent Fabius. Gen. Tlass is seen as the highest-level military defector...