“This alliance should be successful, or destruction will be the fate of the whole region, not a mere one or two countries. We are confident of this [success],” al-Assad told Iran’s Khbar TV, according to Syria’s official news agency SANA.
The agency said the alliance comprises Syria, Russia, Iran and Iraq.
Last year, the United States started an international air campaign in Syria and Iraq against the Islamic State extremist militia, which controls large swathes of territory in both neighbouring countries.
Al-Assad, an ally of Russia, downplayed the significance of the US-led coalition.
“A thief cannot become a policeman to protect a city from thieves. Thus, countries, which support terrorism, cannot combat terrorism,” he said, using a term referring to rebels fighting to oust him.
“The Western officials are living in a state of loss and lack of a clear vision.”
Several Western powers, backing rebels in Syria, have repeatedly called for al-Assad to step down to end the country’s conflict, which has claimed the lives of at least 250,000, according to the UN estimates.
Al-Assad has been in power since 2000.
On Wednesday, Russia started its first airstrikes in Russia, portraying it as aimed at fighting terrorism.
However, the West-backed Syrian opposition has said the Russian airstrikes hit areas controlled by moderate rebels and killed civilians in the country, claims denied by Moscow.
On Sunday, Russian warplanes carried out a new wave of strikes in central Syria, resulting in at least five civilian deaths, monitors reported.
The jets bombed the town of Talbiseh and villages of Ghirnata and Om Sharshouh, north of Syria’s central province of Homs, leaving at least one civilian dead, stated the Local Coordination Committees (LCC), a monitoring group reporting violence inside Syria
The strikes are the latest by Russia in these areas. Opposition groups say there is no Islamic State fighters or al-Qaeda affiliate presence in the area.
Four more civilians were killed in Russian airstrikes in a market near the Islamic State-held area of Akheirbat on the eastern outskirts of the central province of Hama, the LLC added on its Facebook page.
Russian jets also mounted two airstrikes in the town of Jisr al-Sughur in Syria’s north-western province of Idlib, the group said without reporting casualties.
Islamic State is not known to have a presence in this area.
The Russian Defence Ministry said its aircraft had in the past 24 hours mounted 20 flights against Islamic State targets in Idlib and near the radical militia’s stronghold in al-Raqqa in eastern Syria.
The bombing destroyed facilities and ammunition dumps manned by “terrorists” there, the ministry said in an online statement.
Russia insists that its raids in Syria are aimed at the Islamic State and claims that its efforts have significantly weakened the al-Qaeda splinter group.
The Syrian opposition says the Russian strikes are aimed at bolstering al-Assad whose overstretched troops have suffered a series of military setbacks by rebels in recent months.
The Syrian crisis began in 2011 with peaceful anti-government protests and soon developed into a full-blown war.