Prime Minister David Cameron wants Britain to do more to help the United States destroy Islamic State in Syria, he said in an interview broadcast on Sunday.
Britain conducts regular strikes against IS militants in Iraq but has so far limited its Syrian involvement to flying surveillance missions to gather intelligence.
Cameron failed to get parliamentary approval for military action against the forces of Syrian President Bashar al-Assad in 2013 but has asked lawmakers to consider whether Britain should now join U.S.-led strikes against IS in Syria.
"I want Britain to do more, I'll always have to take my parliament with me," Cameron told U.S. network NBC.
"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 to destroy the caliphate in both countries."
Government sources say he is expected to wait until after the opposition Labour Party elects its new leader in September to seek a fresh vote on bombing Syria.
On Friday the Ministry of Defense said British pilots embedded with U.S. and Canadian forces had taken part in air strikes in Syria, angering some lawmakers who said the government had misled parliament.
In a speech on Monday, Cameron will say Britain also needs to do more to confront the ideology of extremism by promoting British values such as democracy, freedom and the rule of law and challenging "ludicrous conspiracy theories" of groups such as IS, also known as Islamic State in Iraq and the Levant (ISIL).
"We must de-glamourise the extremist cause, especially ISIL. This isn't a pioneering movement, it is vicious, brutal, fundamentally abhorrent," he will say, according to extracts released in advance by his office.
He will also issue a warning to those thinking of joining the around 700 Britons already thought to have traveled to Syria and Iraq.
"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. That is the sick and brutal reality of ISIL," he will say.