WASINGTON - US-led coalition troops in Afghanistan will never rid the country of insurgents and won't win the war simply by maintaining a presence in the area, Prime Minister Stephen Harper said in an interview aired Sunday. Harper, speaking to Fareed Zakaria on CNN's GPS programme, said success of the mission in Afghanistan will be measured by the ability to eventually hand over enforcement duties to a reliable Afghan force. "We're not going to win this war just by staying -- we are not ever going to defeat the insurgency," Harper said in the interview, which was recorded during the Prime Minister's visit to New York last week. "My reading of Afghanistan's history is that they've probably had an insurgency forever, of some kind. "A part of the calculation here is ultimately the source of authority in Afghanistan has to be perceived as being indigenous. If it's perceived as being foreign - and I still think we're welcome there - it will always have a significant degree of opposition." Harper, who said he was pleased with renewed commitment of US troops in Afghanistan, said he believed the main issue in Canada was whether the Canadian mission in Afghanistan has been successful and not whether the troops remain in that country beyond its expected withdrawal date in 2011. Speaking to the editorial board of the Wall Street Journal on Saturday, Harper said he felt the success of the NATO mission in Afghanistan would be a test on the military alliance for future operations. "NATO has taken on a United Nations mission and NATO must succeed or I do think the future of NATO as we've known it is in considerable doubt," he told the Wall Street Journal. "We have to get our act together -- or NATO will not be able to undertake these kinds of missions in the future. There may be some around the NATO table who don't think it should. But if that's their position, that's not what they are saying." Canada has about 2,700 soldiers serving in Kandahar in Southern Afghanistan on the NATO-led mission. There have been 108 Canadian soldiers killed in the conflict since Canada's operations started in 2002. Also on Sunday, Zakaria started his segment with Harper by highlighting the fact Canada is the only industrialised nation without a major failure or bailout linked to its banks. Harper said stimulus packages are "essential" at this point, but emphasised the need for a healthy global economy and warned against protectionism when putting any financial relief packages into place. "I had a good visit with President (Barack) Obama and obviously one of the big concerns we have in Canada is not to see the US slide towards protectionism," Harper told CNN. "If we try to have this economy recover by having a series of stimulus packages that are oriented to only stimulating a national economy, or a national economy at the expense of a global economy, we're actually going to drive this thing deeper into recession. "We knew from the 1920s that an unregulated financial sector would lead to pyramid selling and all kinds of equivalent problems, so in a sense we're going back and learning some lessons that I thought had already been learned."