Syrian President Bashar al Assad has criticized Britain's entrance into the U.S.-led coalition attacking Daesh militants in Syria, saying the airstrikes are illegal and will fail, according to Daily Mail.

'It will be harmful and illegal and it will support terrorism, as happened after the coalition started its operation a year or so [ago] because this is like a cancer,' he told the Sunday Times in an interview.

'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 added: 'You cannot defeat them [Daesh] through airstrikes alone. You cannot defeat them without co-operation with forces on the ground.

Assad said if Western and regional support for terrorists ends, then it will take "a matter of months" to end the conflict.

Britain expanded its involvement in the U.S.-led coalition last week from conducting airstrikes solely against Daesh targets in Iraq to bombing the militants in Syria as well after Prime Minister David Cameron lobbied his parliament for approval.

He said the airstrikes would be "part of a wider strategy" to overcome Daesh.

Sources: MENA