Assad dismissed US and France accusations about an alleged chemical attack on August 21 near capital Damascus which they blamed on Syrian government and said it would have made no sense to use chemical weapons in an area where his troops were also fighting.
"Those who make accusations must show evidence. We have challenged the United States and France to come up with a single piece of proof. Obama and Hollande have been incapable of doing so," he said in an interview with French daily Le Figaro.
"Anybody who contributes to the financial and military reinforcement of terrorists is the enemy of the Syrian people. If the policies of the French state are hostile to the Syrian people, the state will be their enemy," he said. "There will be repercussions, negative ones obviously, on French interests."
France has backed the anti-Syria militants since the start of the two-and-a-half year old foreign-backed conflict in Syria.
"The Middle East is a powder keg and the fire is approaching," Assad said, according to extracts of the interview published on Monday.
"We shouldn't just talk about a Syrian response, but what will happen after the first strike. Everybody will lose control of the situation when the powder keg blows."
Tensions rose higher in the region after US rushed to dispatch its warships toward Syria, threatening to bomb several areas in the country, based on conflicting reports of an alleged chemical attack in the country.
The US-backed militants posted pictures and videos of an alleged chemical attack which they claimed the Syrian army was responsible for it.
The Syrian government, which has already called for UN action against several cases of chemical attacks by anti-Syria militants in the country, rejected the claims as baseless and paved the way for visiting UN team of inspectors to investigate the story.
Syria says the attack was actually carried out by the foreign-backed militants to open way for their Western and regional supporters to attack Syria.
Despite killing of at least 100,000 people in the massive insurgency in Syria, the US had said that it would enter the conflict if a chemical attack was carried out.
SHI/SHI