British Prime Minister David Cameron has reportedly dropped plans for a parliamentary vote on extending British airstrikes to Islamic State (ISIS) positions in Syria, dealing what could prove to be a significant blow to the U.S.-led coalition battling ISIS militants in the Middle East.

Various British media outlets, including The Guardian and The Times of London, earlier reported that Cameron was set to put to a vote in the House of Commons a plan for Britain to join the U.S. in conducting more aggressive airstrikes in Syria to enable the U.S.-led coalition to regain its foothold in the region and thus counter the surging Russian presence.

But according to Fox News, these British news outlets reported that Cameron has decided not to push through with his plan.

This came a day after a Foreign Affairs Committee report urged Cameron not to join the airstrikes unless there was a "coherent international strategy" that can realistically defeat ISIS.

"In the absence of such a strategy, taking action to meet the desire to do something is still incoherent," the report said.

Nile Gardiner, director of the Heritage Foundation's Margaret Thatcher Centre for Freedom, told Fox News that the latest developments in London were "very bad news" for the White House.

"This is without a doubt a huge blow to the U.S.-led international coalition in Iraq and Syria," Gardiner said. "Although Britain will continue to play a role in terms of airstrikes in Iraq, Syria is really emerging as the main battleground and so the British move significantly undermines the U.S. position and makes it far harder to build a powerful U.S.-led coalition for military action inside Syria."

The lack of British commitment for a stronger military response against ISIS came just days after US President Barack Obama authorised the deployment of a limited number of Special Operations forces to Syria to help revitalise the struggling US-led campaign against ISIS.

An earlier blow was struck by Canada, another key U.S. ally, which announced that it is withdrawing its fighter jets in the fight against ISIS in both Iraq and Syria following the swearing into office of new Liberal Canadian Prime Minister Justin Trudeau.

As the US-led coalition appears to be wavering, Russia continues to strengthen its presence in the region.

On Thursday, the Daily Express reported that Moscow has sent missile systems to Syria to protect its military forces in the war-torn country on top of 6,000 more troops to guard Russian military forces in Syria.

Colonel General Viktor Bondarev, the head of Russia's air force, said they are sending the missile systems based on the possibility that Russian fighter jets in Syria could be hijacked by ISIS militants and used against Russian forces.

"We have calculated all possible threats. We have sent not only fighter jets, bombers and helicopters, but also missile systems. We must be ready," Bondarev said.