"If the Europeans deliver weapons, then Europe's backyard will become terrorist, and Europe will pay the price for it," he was quoted as telling German daily the Frankfurter Allgemeine Zeitung.
Sending weapons to rebels would lead to terrorism in Europe, he said in an exclusive interview to appear in Tuesday's edition of the newspaper.
"Terrorists will return, battle-hardened and with an extremist ideology," he was quoted as saying.
Assad also denied US, British and French claims that his forces had used chemical weapons against his people during the escalating conflict in Syria.
"If Paris, London and Washington had any evidence for their claims, they would have submitted it to the global public," said Assad, whose comments were published in German.
The conflict in Syria was set to dominate a G8 summit starting in Northern Ireland on Monday, with the Assad regime's ally Moscow expected to come under pressure from Western powers.
Assad also labelled the insurgents as terrorists and denied any blame for the escalation of the conflict, while defending cooperation with Russia and Iran as legitimate support.
Washington said last week it would provide Syria's rebels with military support after it determined that the regime had used chemical weapons.
Both London and Paris have discussed the possibility of sending weapons to the fighters that are battling the Syrian government after the EU lifted an arms embargo.