Canada's foreign minister has told Nato that the alliance's other members must provide more support to the military operation in southern Afghanistan.
Canadian casualties have decreased support for the mission
Peter Mackay said that even a handful of countries could not do "all that is necessary" to provide the secure environment which was needed.
The country's defence minister has admitted that their 2,000-strong troop deployment is stretched to capacity.
Some 42 Canadian soldiers have died in Afghanistan since 2002.
The BBC's Lee Carter says Ottawa is growing increasingly frustrated over the unwillingness of mainly European Nato members to deploy troops to help fight mounting Taleban resistance.
Mr Mackay said he had warned Nato's Secretary General Jaap Hoop de Scheffer that the current situation, in terms of military deployment, could not go on.
He said: "But my point to him [Mr Hoop de Scheffer] was that we cannot continue to do this, without further support.
"No one country, or even a handful of countries, can do all that is necessary to provide the kind of secure environment needed in the other parts of the mission."
Carter said such disenchantment was also being felt on the ground in Kandahar, with soldiers airing concerns on Canadian radio.
He added that Mr Mackay's plea comes as the country's conservative government grapples with declining public support for the mission.
Carter said: "The sight of flag-draped coffins arriving back home has been a shocking one in a country that for the past few decades has traditionally been involved in peacekeeping missions.
"But over the past few weeks there have also been emotional rallies of support for the troops in Afghanistan, held in several Canadian cities."