LONDON - Britain’s parliament looks set to vote in favour of joining air strikes on Islamic State (IS) jihadists in Syria Wednesday despite angry exchanges which have exposed deep divisions on military action.

Prime Minister David Cameron kicked off over 10 hours of debate by urging MPs to “answer the call” from allies like France and the US, adding that bombing the “mediaeval monsters” of IS was “the right thing to do”. “The question is this: do we work with our allies to degrade and destroy this threat... or do we sit back and wait for them to attack us?” he told the House of Commons.

Ministers and sources in the main opposition Labour party believe Cameron will win the vote expected at around 2230 GMT, paving the way for Britain to join air strikes on Syria within days or even hours.

But many of the MPs crammed on to the Commons’ benches and walkways spoke against air strikes while thousands of anti-war protesters are expected to protest outside parliament later for the second night running. A new opinion poll Wednesday suggested that public support for joining air strikes in Syria had dropped significantly in recent days.

A YouGov poll in The Times newspaper found that 48 percent of Britons supported Syria strikes compared to 59 percent last week. Labour leader Jeremy Corbyn, who opposes military action, condemned Cameron’s “ill thought-out rush to war” and said his proposals “simply do not stack up”. “The spectre of Iraq, Afghanistan and Libya looms over this debate,” Corbyn added, referring to unpopular British interventions in foreign conflicts over the last 15 years.

Cameron urged MPs not to let the memory of Iraq — which many Britons believe a Labour government under Tony Blair led them into using “sexed up” evidence on weapons of mass destruction — to dictate their decision. “This is not 2003. We must not use past mistakes as an excuse for indifference or inaction,” he added. The prime minister faced repeated calls during a raucous debate to apologise after reportedly telling Conservative MPs not to vote with “a bunch of terrorist sympathisers” against the strikes.

Cameron has wanted to extend Britain’s role in the fight against IS for months but made a fresh push which led to the vote after last month’s Paris attacks which killed 130 people.

Britain already has eight Tornado fighter jets plus drones involved in the US-led coalition striking IS targets in Iraq. However, it currently only conducts surveillance and intelligence missions over Syria. The government will deploy more jets if the bombing is approved and argues that the Royal Air Force’s Brimstone missiles will be particularly valuable for precision strikes to avoid civilian casualties.

US Secretary of State John Kerry praised Cameron for bringing the vote to parliament Wednesday and urged all NATO countries to “step up support” for the fight against IS. Military experts question how much difference Britain would make to the campaign, saying it may be more about wanting to stand shoulder-to-shoulder with allies like France and the United States.

Cameron again stressed that British ground forces will not be deployed to Syria as part of the action Wednesday, saying that would be a “mistake”. Labour is deeply divided on air strikes . Corbyn opposes the move but has let his party have a free vote on the issue because dozens of his MPs, including his foreign and defence spokespeople, want to support it.

A Labour source speaking on condition of anonymity said he expected around 40 of its MPs to support the bombing. “It’s expected that the government will win this vote... but it’s definitely lost the argument,” another Labour source added.

As well as Labour and the next biggest Commons grouping, the Scottish National Party, a handful of lawmakers from Cameron’s own Conservative party also oppose joining air strikes .

Cameron also fleshed out his claim that there were 70,000 moderate opposition fighters in Syria ready to help fight against IS.

He said these were mostly members of the rebel Free Syrian Army but added there were 20,000 Kurdish forces ready to contribute. He conceded that, while they were not “ideal partners” and “some of them do have views that we don’t agree with”, they could “play a role” in the future of Syria.