British MPs began debating on Friday morning whether to join a US-led air campaign against the "Islamic State" jihadist group. In pushing for support, British Prime Minister David Cameron warned the military action within a coalition of Western and Arab nations would take "years."

"This is going to be a mission that will take not just months but years, but I believe we have to be prepared for that commitment," said Cameron.

He urged a call to action against the "psychopathic terrorists" who, so far, have beheaded British aid worker David Haines and American journalists James Foley and Steven Sotloff. An IS supporter group beheaded French citizen Herve Gourdel in Algeria earlier this week.

Cameron said that taking action was not only a matter of dealing with atrocities committed in Iraq, but protecting Britain's streets, which "should not be a task that we are prepared to entirely subcontract to other air forces."

The IS began the executions in August as revenge against countries who are contributing to the US-led air strikes in Iraq and Syria.

On Friday, the US military said warplanes destroyed four IS tanks outside the city of Deir el-Zour, targeting a key oil-producing area that has generated millions of dollars for the militant group.

Syria out of the British picture - for now

British lawmakers are expected to approve strikes against the Sunni militants in Iraq, but not Syria. Cameron does not need Parliament's approval for the airstrikes, but he is cautious about launching military action after losing a parliamentary vote last year to carry out strikes against Syria.

Prior to the debate, British Foreign Secretary Philip Hammond said Parliament would be consulted if the British strikes would be extended to Syria. But members of Cameron's own party have questioned the scope of the operation and the possibility of British deaths in conflict.

"Simply allowing ISIL (another term for the IS group) to retreat across an invisible border, which they control, into Syria and regroup is simply no answer," said Peter Hain, a former senior member of Blair's Labour government.

Britain would join the US, France and Denmark in launching targeted airstrikes on the IS in Iraq, where, like in Syria, they control large swathes of territory. Belgium and the Netherlands are also debating whether to commit warplanes too. Denmark's government approved its involvement on Friday.

"No one should be ducking in this case," said Danish Prime Minister Helle Thorning-Schmidt. "Everyone should contribute."

Britain's vote is due at 1600 (GMT).

jr/kms (AFP, dpa)