Behind closed doors, Canadian officials are working feverishly to prepare for Canadian jets to strike targets inside Syria, CBC News has learned.

Sources have told CBC that Canada is close to clearing away “the legal hurdles” that stand in the way of extending the combat mission from Iraq into Syria, should the government decide to expand the mission.

The legal case is critical, because, unlike Iraq, whose government invited Canada and its coalition partners to join the fight against ISIS, Syria under its leader Bashar al-Assad is considered an enemy. The U.S. has laws that allow it to engage in pre-emptive strikes in a sovereign nation, but Canada does not.

"We have, out of necessity, had these discussions with our allies," Justice Minister Peter MacKay told CBC Radio’s The House when asked if preparations are being made to hit ISIS targets in Syria.

"We're operating against an enemy that does not respect any borders,” he said.

"We want to degrade and cripple their ability and with that objective, we at the Department of Justice are obviously working with other departments to examine certain scenarios,” said MacKay, who also pointed out that they are “not there yet.”

CF-18s 'ready,' for Syrian strike

Sending more signals that Canada is looking to expand its mission, Defence Minister Rob Nicholson told a Halifax International Security Forum audience that “the door is not closed” to Canada attacking targets in Syria.

U.S. Senator John McCain, left, is greeted as he arrives at the opening session of the Halifax International Security Forum in Halifax on Friday. (Andrew Vaughan/Canadian Press)

If the legal case is made and the government does decide to attack ISIS targets in Syria, Chief of the Defence Staff Gen. Tom Lawson says the CF-18s are prepared.

“We would be ready for that,” Lawson told CBC Radio’s The House.

Lawson said that the military is already prepared for a much longer mission. “We are absolutely prepared to meet the government’s needs should they decide to commit Canadian troops and Canadian aircraft for a longer period,” he said.

The government has not revealed details about the cost of the Iraq mission, but Lawson said he has provided the figures.

“We provided an estimate to the government,” he said. “I’ll leave it to our elected officials to determine when that will be shared.”

John McCain says Iraq mission is 'delusional'

But as Lawson and Nicholson defended the coalition strategy against ISIS, Republican U.S. Senator John McCain arrived at the Halifax International Security Forum with a blistering rebuttal, dismissing the current mission and Canada’s six-month assessment period as “delusional.”

“It's not realistic,” McCain told CBC Radio’s The House.

"It's delusional to say you're going to treat ISIS one way when they're in Iraq and another way when they're in Syria. That's foolish," he said.

When asked about the current strategy of coalition airstrikes supported by Iraqi boots on the ground, McCain, who will be the chair of the Senate armed services committee when Congress reconvenes in January, compared it to the American fiasco in Vietnam.

"There is no strategy that any military person I know believes will succeed in the present stated goal, which is to degrade and defeat ISIS,” McCain said.

McCain argues that a significant number of Western military soldiers will be needed in both Iraq and Syria to stabilize those countries.