Maj. Gen. Mohammed Ezz al-Din Khalouf told Al-Arabiya TV that many of those still with Assad's regime have lost faith in it.
"It not an issue of belief or practicing one's role," he said. "It's for appearance's sake, to present an image to the international community from the regime that it pulls together all parts of Syrian society under this regime."
Activist videos posted online Saturday showed Khalouf sitting with a rebel fighter after his defection and riding in a car to what the video said was the Jordanian border.
The video said he was Chief of Staff for the army branch that deals with supplies and fuel.
While widespread defections from the Syrian army have sapped it of much of its manpower during the two-year-old anti-Assad uprising, high-level defections have been rare.
The Syrian government did not comment on the defection.