Syrian President Bashar al-Assad warned Washington in an interview published on Monday in Russia that any U.S. military intervention in Syria would fail and denied that his forces had used chemical weapons.
"Failure awaits the United States as in all previous wars it has unleashed, starting with Vietnam and up to the present day," he told the pro-Kremlin Izvestia newspaper in an interview which the Russian daily said was conducted in Damascus.
Assad said Syrian government forces had been close to the area, in suburbs of Damascus, where rebel forces accused his troops of firing poison gas projectiles last week, and there was no clear front line there.
"Would any state use chemical or any other weapons of mass destruction in a place where its own forces are concentrated? That would go against elementary logic," Assad told Izvestia.
"So, accusations of this kind are entirely political and the reason for them is the government forces' series of victories over the terrorists," he said, referring to rebels fighting in the two-year-old civil war.
Dismissing the chemical weapons accusations as "nonsense" and "unsubstantiated", he said the United States, Britain and France had long sought to justify a military intervention in Syria.
Russia has been Assad's most important international ally during the conflict, supplying his troops with arms and resisting pressure at the United Nations for tighter sanctions on Damascus.
Russian Foreign Minister Sergei Lavrov told U.S. Secretary of State John Kerry by telephone on Sunday that Moscow was deeply concerned about the possibility of any U.S. military intervention in Syria, a ministry statement said.
Washington has faced growing calls for action in response to Wednesday's gas attack. President Barack Obama previously declared that any use of chemical weapons in Syria would be a "red line" which would require a firm response.
U.N. inspectors left central Damascus on Monday to examine sites of the chemical attack, a Reuters witness said, after calls from Western powers for military action to punish what may be the world's worst poison gas strike in 25 years. Opposition activists estimate that from 500 to well over 1,000 people died in the gassing.
Assad said Russia's military support had helped Syria cope with international economic sanctions and cited unspecified contracts with Russian companies which he said were helping Damascus. He gave no details except to say that such contracts helped Syrians get "basic products" needed for survival.
Asked about the arms deliveries, Assad said: "I want to say that all contracts that have been concluded with Russia are being fulfilled."
He gave no details and did not say whether Damascus had taken delivery of advanced S-300 air defense systems from Russia which could vastly enhance its defensive capabilities.
(Reporting by Katya Golubkova, writing by Timothy Heritage; editing by Mark Heinrich)