"I address you...as one of the Syrian Arab army's sons who reject the criminal behaviour of this corrupt regime. The honourable people in the military would not accept these crimes," Tlas said in a televised statement on al-Arabiya television.
The comments were his first to be aired publicly since Tlas, a rare Sunni Muslim member of President Bashar al-Assad's mostly alawite inner circle and a senior officer in the Republican Guards, defected earlier this month.
Tlas, whose father Mustafa Tlas was Syria's defence minister for 32 years and confidante of Assad's father, the late President Hafez al-Assad, did not call outright for soldiers to defect, unlike scores of senior Sunni officers who have abandoned the army since the 16 month uprising.
He said preserving national unity was a priority in a post-Assad era.
"While I ask God to rest the soul of the martyrs of this great revolution, I call upon you to do the impossible to preserve the unity of Syria...
"Our duty today as Syrians is to assure each other and deny the opportunity for this regime and everyone who wants to fuel conflict between us as Syrians," Tlas said from an undisclosed location.
The officer corps of the Syrian army is mostly composed of members of Assad's Alawite sect, an offshoot of Shi'ite Islam, which has dominated the power structure in the mostly Sunni country for the last five decades.
Sunni officers in the army usually hold administrative posts and are closely watched by the mostly Alawite intelligence apparatus.