In a lengthy interview with the Venezuelan network TelSUR Wednesday, Assad said he is not confident Syrian cooperation in an investigation of the August chemical attack on Damascus' suburbs will head off a U.S. military strike.
The 40-minute interview was posted on Syriaonline.syr.
U.S. President Barack Obama's speech at the U.N. General Assembly was "full of allegations based on fabrications and lies," Assad said.
"Since the beginning of the Syrian crisis, American policy whether knowingly or unknowingly has been based on lies," Assad said.
"The administration played a direct role in these fabrications after the chemical weapons issue was raised on Aug. 21. The administration has not provided any evidence to support its claims, which implies it was lying to the American people."
Assad said he has heard confessions from rebels -- admitting they brought chemical agents from neighboring countries into Syria -- and said the confessions were broadcast on state television a week ago.
"We provided the evidence to the Russian government before the U.N. mission came to Syria," he said.
Assad also criticized U.S. officials for taking Syria to task for chemical weapons and Iran to task for its nuclear program when it never has addressed Israel's alleged nuclear arsenal. Israel does not acknowledge it has nuclear weapons although there have been allegations it produced such weapons in the 1970s.
Syria asked the U.N. chemical weapons experts to return to Syria to assess the Syrian stockpile but warned "terrorists" may interfere with their work.
Assad said Syria already has sent details of its chemical arsenal to the Organization for the Prohibition of Chemical Weapons and accused "terrorists" operating inside Syria of being financed and "instigated by people" outside the country with the aim "of pushing Syrians towards complete despair."
The Lebanese daily al-Akhbar reported Assad later boasted he has weapons more powerful than chemical weapons for use against Israel.
"Initially we manufactured chemicals arms as a deterrent weapon to confront Israel's nuclear arsenal. Now, they are no longer a deterrent weapon," Assad told reporters in Damascus.
"Today we have more important and more sophisticated weapons that can blind Israel in a moment."
Syria's civil war began in March 2011 and estimates put the death toll at more than 100,000 and the displaced in the millions.