Parliament is to be recalled on Friday to discuss the UK’s possible involvement in air strikes against Islamic State (IS) in Iraq.
Prime Minister David Cameron said MPs should respond to the Iraqi government’s request for help.
He added that the UK “should not turn away from what needs to be done”.
The Liberal Democrats are backing air strikes in Iraq and Labour leader Ed Miliband has confirmed his support, saying the UK cannot “opt out”.
Meanwhile, the Foreign Office has said it is “aware” of reports that a British national has died in Syria, but it has “no further information at this moment”.
IS – also known as Isil – has taken control of large areas of Iraq and Syria in recent months and seized several Western hostages.
It has threatened to kill British aid worker Alan Henning, having released footage of the killing of another British man, David Haines, earlier this month.
Mr Cameron, who is in the US, tweeted: “I have requested that Parliament be recalled to debate the UK response to the Iraqi Govt’s request for support against Isil. The Speaker has accepted my request to recall Parliament on Friday.”
He later said: “What we are doing is legal and it is right. It does not involve British combat troops on the ground.”
He added that “when we are threatened in this way, we should not turn away from what needs to be done”.
“I’m confident we will get this through on an all-party basis,” Mr Cameron said.
“If there was a question of taking action against Isil in Syria, it would be a separate parliamentary debate. I want to be very clear about that.”
Deputy Prime Minister and Liberal Democrat leader Nick Clegg told the BBC his party would support air strikes in Iraq.
He said they were “legal” and the UK would be “part of a much bigger coalition, a whole array of countries, crucially including a number of Arab countries which deprives Isil of the ability to somehow portray it as a west verses the rest crusade”.
Thanks for reading,