Prime Minister David Cameron and Iranian president Hassan Rouhani are meeting in person for the first time ever to discuss Iran's role in fighting the Islamic State (IS).

Meeting later in New York, it is thought Cameron will use the opportunity to persuade Rouhani Iran should join action against IS militants. No British prime minister and Iranian president have met since the Iranian revolution of 1979.

IS has become notorious for the brutal methods it adopts as it tries to establish a “caliphate”, or religious state, in Syria and northern Iraq.

Pressure to target the extremist group has been mounting, and today the US and its allies launched its first airstrikes against them in Syria – so far they had been limited to northern Iraq.

But the UK government separately confirmed it has not yet joined the strikes in Syria. According to the BBC, a Ministry of Defence spokeswoman said “The UK has not committed anything yet. Conversations are ongoing. There might potentially be an update in the coming days. We have not ruled ourselves out."

Exactly what Cameron will propose to Rouhani in terms of Iranian involvement is not yet clear. "Coming at a time when the Obama administration has said Iran has a role to play in combating IS, Mr Cameron is expected to gauge what form that might take," BBC correspondent Nick Bryant said.