President Bashar al-Assad claimed Western powers are "becoming much weaker" in Syria, in a confident interview published in The Sunday Times.
"In the past if I said anything, people would say the Syrian president is disconnected from reality. Now it's different. The West is becoming much weaker," told the British weekly.
"They don't have a leg to stand on explaining to people what's going on.
"Isis (the Islamic State group) was smuggling oil and using Iraqi oilfields under American satellites and drones to make money, and the West was not saying anything.
"Whereas here the Russians interfered and Isis started to shrink in every sense of the word."
Assad acknowledged the key role played by Russian airstrikes, saying: "What made the difference, of course, was firepower. They have firepower we don't have."
He added: "At the end we were fighting an unlimited reserve of terrorists coming to Syria and we struggled, so Russian firepower and Iranian support has compensated."
However, he said of the Russians: "They never try to interfere because they don't want anything from us. They don't ask us to be a puppet president."
Assad also confirmed his determination to crush rebel forces in Aleppo, the one-time economic powerhouse that has been under a three-month government siege.
"Aleppo is an issue where terrorists have occupied part of the city, and we need to get rid of them," he said.
More than 300,000 people have been killed in Syria since the conflict erupted with anti-government protests in March 2011, and the situation for civilians in Aleppo is particularly dire.
Asked if he could sleep with the knowledge of the children being killed every day in Aleppo and elsewhere, Assad laughed and said: "I know the meaning of that question.
"I sleep regular, I sleep and work and eat normal and do sports."
