"I want Britain to do more, I'll always have to take my parliament with me," British Prime Minister David Cameron told US network NBC in an interview airing Sunday.

"We have to destroy this caliphate, whether it is in Iraq or in Syria," he added. "That is a key part of defeating this terrorist scourge that we face."

The UK has been conducting regular airstrikes against jihadist "Islamic State" (IS) militants in Iraq since getting parliamentary approval for the move last September. Its involvement in Syria, on the other hand, has largely been limited to surveillance missions and air-to-air refueling.

"We are talking and discussing at the moment, including with the opposition parties in Britain, what more we can do. But be in no doubt we are committed to working with you," Cameron said.

In 2013, Cameron failed to get parliament's backing to take military action against the forces of Syrian President Bashar al-Assad. Government sources cited by Reuters say Cameron is expected to wait until a new leader of the opposition Labour Party is elected in September before seeking a fresh vote on whether Britain should join US-led strikes in Syria against IS.

Although the British military doesn't have parliamentary permission to bomb the jihadists in Syria, revelations surfaced on Friday that UK pilots had been embedded with US and Canadian forces carrying out airstrikes there. The disclosure angered some lawmakers, who accused the government of going back on promises to seek a parliamentary mandate before taking such action.

'Vicious, brutal' movement

Cameron's NBC interview comes ahead of a Monday address in which he is expected to outline his government's anti-terrorism strategy for the next five years. According to speech extracts released early by the prime minister's office, Cameron will issue a warning to young people who are considering joining IS.

"This isn't a pioneering movement; it is vicious, brutal, fundamentally abhorrent," he will say. "You are cannon fodder for them. They will use you. If you are a boy, they will brainwash you, strap bombs to your body and blow you up. If you are a girl, they will enslave and abuse you.”

Some 700 Britons are already thought to have traveled to Syria and Iraq to fight alongside IS, which seized large chunks of territory in both countries after a rapid advance last summer.

The group says it aims to set up an Islamic "caliphate" across the Middle East.

nm/tj (Reuters, AP, dpa)