An ISIS militant uses a loud-hailer to announce to residents of Taqba city that Tabqa air base has fallen to ISIS militants, in nearby Raqqa city.

Strikes against the Islamic State of Iraq and Syria (ISIS) inside Syria could be launched without an invitation from the Syrian government, British Prime Minister David Cameron said Thursday, raising one of the first justifications for foreign military action in Syria without the government’s consent.

Speaking at the start of this week’s NATO summit in Wales, Cameron suggested that under international law, the West does not need an invitation from Syrian President Bashar al-Assad to attack ISIS within Syrian borders due to the illegitimacy of his government, according to a report in The Guardian.

Describing ISIS as a direct threat to the UK, Cameron also stepped up his case for British involvement in U.S. airstrikes against ISIS targets in Iraq, although he stopped short of declaring his country would definitely join the U.S. mission.

The prime minister also indicated his interest in forming an international coalition to carry out operations in Iraq. Since late August, Washington has been pushing for an international campaign against ISIS, including attempts to recruit partners for potential joint military action.

Meanwhile, NATO also appeared to have a change of heart on Thursday, when its secretary-general said it would “seriously” consider any requests from the Iraqi government for assistance in fighting ISIS.

The statement from Anders Fogh Rasmussen came as the 28-member political and military alliance opened a two-day summit in Wales. But his comments contradicted early remarks made by Rasmussen in June, when he said that the alliance did not see any role in Iraq after ISIS militants seized a large swath of territories in the north and west of the country.

While the official agenda will focus on the crisis in Ukraine and the drawdown of the NATO combat mission in Afghanistan, the rise of ISIS is expected to dominate discussion on the sidelines of the high-stakes meeting.

Rasmussen’s statement also comes after U.S. President Barack Obama and British Prime Minister David Cameron declared Thursday that their countries would “not be cowed” by ISIS extremists, after a second American journalist was confirmed dead from an execution-style killing by an ISIS militant.

“We will be more forthright in the defense of our values, not least because a world of greater freedom is a fundamental part of how we keep our people safe,” the leaders wrote in a joint editorial in the Times of London.

The U.S. began airstrikes against ISIS targets in Iraq last month, and both the U.S. and Britain have been making humanitarian aid deliveries to besieged minority groups in the region.

Cameron said Monday he had not ruled out joining the U.S. in airstrikes, but added that the priority was to support those already fighting the militants on the ground.

Meanwhile, NATO member Germany has already started arming the Kurdish forces, known as the Peshmerga, to fight ISIS. It announced its decision to deliver enough weapons to arm 4,000 Peshmerga, who are widely regarded as one of the most effective military forces on the ground in Iraq fighting ISIS, on August 31.

Late August, U.S. defense secretary Chuck Hagel hailed the UK, France, Canada, Croatia, Denmark, Italy and Albania for arming the Kurdish peshmerga, and said he expected other nations to contribute.

 
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