In an interview, Mr Assad called Turkish Prime Minister Tayyip Erdogan "bigoted" and said Ankara was allowing terrorists to cross into Syria to attack the army and Syrian civilians.
"It is not possible to put terrorism in your pocket and use it as a card because it is like a scorpion which won't hesitate to sting you at the first opportunity," Mr Assad said.
"In the near future, these terrorists will have an impact on Turkey and Turkey will pay a heavy price for it."
Turkey, which shares a560-mile border with Syria and has Nato's second largest deployable armed forces, is one of Assad's fiercest critics and a staunch supporter of the opposition, although it denies arming the rebels.
It shelters about a quarter of the two million people who have fled Syria.