Canadian Prime Minister Stephen Harper says Western forces alone won't defeat the Taliban insurgency in Afghanistan, and that the US must have a viable exit plan before asking other countries to do more there. "Frankly, we are not going to ever defeat the insurgency," Harper said in an interview that aired Sunday on CNN. "My reading of Afghanistan history is that's it's probably had an insurgency forever of some kind." Canadian and other NATO troops have made some gains against the insurgents over the years but those gains are not irreversible and the overall success has been modest, Harper said. "What has to happen in Afghanistan is we have to have an Afghan government that is capable of managing that insurgency," he said. If a foreign power is perceived as the source of authority, "it will always have a significant degree of opposition," he said.