Turkish soldiers stand guard near the Mursitpinar border gate in Suruc, Sanliurfa province, Turkey, as Syrian Kurds wait in tents behind the border fences to cross into Turkey, June 27, 2015.[Photo/Agencies]

LONDON - Prime Minister David Cameron asked lawmakers to consider whether Britain should join US-led air strikes against Islamic State militants in Syria, but his spokeswoman said he hadn't yet decided whether to push for a parliamentary vote on the issue.

Britain conducts regular attacks in neighbouring Iraq and flies drones over Syria to gather intelligence on the group. But unlike some other coalition partners it does not target Islamic State positions in Syria as Cameron failed to get the go-ahead from parliament to do that in 2013.

The death of 30 Britons in an Islamist attack in Tunisia last week has changed the calculus, prompting Cameron, via his spokeswoman, to ask lawmakers to start thinking about whether they would back wider action.

"What has changed is the growing evidence that ISIL (Islamic State) poses a threat to people here in Britain and our national security," Cameron's spokeswoman told reporters on Thursday.

"And in that context the prime minister does think that MPs (lawmakers) should be thinking about these issues. His view is that there has been and continues to be a case for doing more in Syria."

Cameron, who was visibly shaken after losing the 2013 Syria vote, wants to be sure he can win any vote in parliament this time and so is not expected to call a vote until after the summer so he can gauge the support of the opposition Labour Party which is in the throes of choosing a new leader.