After weeks of largely staying on the sidelines of a U.S.-led air campaign against Islamic State fighters, Britain moved toward a more direct military intervention Wednesday when Prime Minister David Cameron recalled Parliament to debate airstrikes.

The debate, slated for Friday, will probably yield approval for British strikes against Islamic State targets in Iraq, following a request for assistance from the Iraqi government. But, notably, Britain will not consider an expanded campaign that would include targets in Syria.

Cameron told the BBC he was confident that a vote on direct military action in Iraq would pass Friday and said he was convinced that the Islamic State represents “a direct threat to Britain.”

“When we are threatened in this way, we should not turn away from what needs to be done,” he said.

Still, Cameron stressed that Britain’s air campaign would stop at Iraq’s border with Syria and that any consideration of expanding strikes in Syrian territory would require a separate debate.

The Netherlands announced Wednesday that it, too, would join the air campaign in Iraq, with officials saying that six F-16 fighter jets would be deployed. The French began carrying out strikes in Iraq last week.

Cameron’s decision to recall Parliament ends weeks of British reluctance to participate in the airstrikes — an unusual stance for a country that prides itself on being Washington’s closest ally and has repeatedly joined the United States in military operations around the globe.

The delay has had far more to do with domestic politics than with any gap in the “special relationship,” analysts say.

Britain has supplied the United States with intelligence and surveillance support and has provided arms to Kurdish forces fighting Islamic State militants. Cameron, meanwhile, has publicly supported the U.S.-led strikes.

But the prime minister has not been willing to seek Parliament’s approval for more direct British military intervention until he knew he had the votes — a lesson learned last year when the House of Commons defeated a proposal for airstrikes against the government of Syrian President Bashar al-Assad.

“He doesn’t want a repeat of what he did last year, which was to panic, recall Parliament and fail,” said Patricia Lewis, director of research in international security for the London-based think tank Chatham House.

Now, however, the stars appear to be aligning for parliamentary support.

When U.S. airstrikes in Iraq began last month, the British public was divided over whether the nation should participate. But in recent weeks, after the release of Islamic State videos showing the beheadings of two American journalists and a British aid worker, public opinion has swung strongly in favor of a more direct British role in combating the group.

Participation in the latest round of airstrikes by five Arab countries — Jordan, Saudi Arabia, Qatar, the United Arab Emirates and Bahrain — has also contributed to rising support here for the campaign.

Still, there appear to be clear limits to the British appetite for intervention. While Cameron seems to have the backing he needs for airstrikes in Iraq, there is much less consensus over the prospect of attacking targets in Syria, where the government has denounced strikes carried out without its consent.

On Wednesday, the leader of the opposition Labor Party, Ed Miliband, endorsed strikes in Iraq, saying Britain cannot “opt out.” But he said his party would not support airstrikes in Syria without a U.N. resolution.

“There will be great support for airstrikes in Iraq,” Lewis said. “The division will be over Syria.”

The French have faced a similar quandary. While France struck targets in Iraq last week, it has refrained from attacking in Syria for fear of appearing to support Assad by helping to eliminate his enemies.

But Dominique Moisi, a founder of the French Institute of International Relations, said that French abstention from the Syria campaign may only be “a temporary moment” and that there is an “interventionist mood” in France.

“If action continues in Syria, it would be very difficult for the French not to join that,” he said. “So, [French leaders] will explain that given the inhumanity of the Islamic State fighters, there is a need to tackle them, wherever is needed, and of course, it’s as much needed in Syria as it is in Iraq.”

Moisi said that because France did not take part in the 2003 invasion of Iraq, it was easier to persuade the French to sign up for airstrikes today than it is to convince the British, who were on the front lines of the 2003 campaign along with the Americans.

“We know how to distinguish a right intervention from a wrong one, a war of necessity from a war of choice — at least that is the mood,” Moisi said.

That mood is likely to harden after the emergence of video Wednesday showing the beheading of a French tourist at the hands of a militant Algerian group that has sworn allegiance to the Islamic State. The tourist, Hervé Gourdel, 55, was kidnapped Sunday while hiking outside the capital, Algiers.

French President François Hollande confirmed the veracity of the video and said Gourdel was killed by Jund al-Khilafah — the Caliphate’s Soldiers — because of the French role in combating terrorism.

French and British airstrikes are more important for their symbolism than they are for any tactical military reason. President Obama has been eager to present the U.S.-led campaign as a collective effort. European support is seen as particularly important at a time when the continent is feeling threatened by the prospect of young Europeans traveling to the Middle East to fight and returning to carry out terrorist attacks.

“These people want to kill us,” Cameron told NBC. “They’ve got us in their sights, and we have to put together this coalition . . . to make sure that we ultimately destroy this evil organization.”