Liberal MP Bob Rae said the New Democratic Party's belief that Canadian troops could somehow be involved in diplomacy in Afghanistan after withdrawing from the military mission is "complete and total fantasy."

NDP Leader Jack Layton jumped on British Brig.-Gen. Mark Carleton-Smith's comments to a newspaper over the weekend that Western forces will never win against insurgents and negotiations with the Taliban might be needed.

Layton expressed support for negotiations, and vowed an NDP government would pull out Canada's 2,500 troops and "launch a diplomatic offensive."

Speaking at a Halifax restaurant Monday, Rae scoffed at the NDP proposal and suggested Layton ignored the military commander's remark that the NATO-led coalition force must remain in the region to allow diplomacy and development to occur.

"He suggested that if we pulled our troops out instantly, that there would somehow be a diplomatic job for Canada to do.… It's a complete and total fantasy," said Rae, the party's foreign affairs critic.

The former NDP Ontario premier said Canada can't abandon its promises to its NATO allies and the Afghanistan government.

"His view underestimates the fact that Canada's membership in NATO carries with it obligations. You can't just come and go. You can't just say, we're here today and gone tomorrow," he said.

"Our aid work and our assistance in training the Afghan army and the police can't be done without having troops on the ground to do their job."

Speaking in Ottawa at a campaign event, Conservative Leader Stephen Harper reacted to the commander's comments by saying he doesn't expect the NATO mission will completely end the insurgency, but rather that it will build up Afghan troops so they can take over.

"The idea that we would eradicate it in just a few short years is unrealistic," Harper said in Ottawa, where he pledged improvements to the universal child care benefit.

He said Afghan President Hamid Karzai has always been open to talking to the Taliban, provided they are willing to participate in the democratic and constitutional process.

"That's very different than simply throwing down arms and letting the Taliban take over the country — which is certainly not what we're proposing."

With files from the Canadian Press