Syrian president Bashar al-Assad has described British air strikes against Islamic State in Syria as “illegal” and says it will only cause “terrorism” to spread.
British MPs voted on last week to join the US-led bombing campaign over Syria.
In an interview with UK media, Mr Assad contrasted Britain’s approach with Russia, which has the backing of the Syrian government.
“It will be harmful and illegal and it will support terrorism as happened after the coalition started its operation a year or so [ago],” he told The Sunday Times.
Terror, he said, was like a cancer which needed to be tackled with a “comprehensive” strategy which would involve working with troops on the ground.
“You cannot cut out part of the cancer. You have to extract it. This kind of operation is like cutting out part of the cancer. That will make it spread in the body faster,” he said.
“You cannot defeat [IS] through air strikes alone. You cannot defeat them without cooperation with forces on the ground. You cannot defeat them if you do not have buy-in from the general public and the government.
“They are going to fail again.”
Britain began its bombing campaign early on Thursday, hitting an oil field held by IS just hours after a decisive parliamentary vote authorised air strikes.
Momentum to join the air campaign grew after IS militants claimed a deadly series of attacks on Paris last month which killed 130 people and wounded more than 350.
In late September, Russia began its own bombing campaign in Syria in support of Mr Assad, more than a year after a US-led coalition began its strikes targeting the IS group.
Russia is coordinating its air strikes with Damascus, unlike the US-led coalition, whose action has been criticised by Mr Assad and his government as ineffectual.
Meanwhile, at least 32 Islamic State fighters were killed and 40 more wounded in air strikes in Syria’s Raqqa province on Sunday, the monitoring group Syrian Observatory for Human Rights said.
The strikes were believed to have been carried out by the US-led coalition targeting the jihadists.
Raqqa is Islamic State’s Syrian stronghold.
Syrian opposition groups will gather in Saudi Arabia on Tuesday to unify their stance ahead of potential talks with the Mr Assad’s government.
It will be the first time representatives of the political opposition and military factions fighting the regime have come together since the conflict began in 2011.
More than 250,000 people have been killed since the Syrian conflict erupted in March 2011 with protests against Mr Assad’s regime.