OTTAWA (Reuters) - U.S. Defense Secretary Leon Panetta said on Tuesday it was important for NATO-led forces to continue implementing their strategy to end the conflict in Afghanistan despite growing signs of public fatigue after 10 years of war. "We cannot fight wars by polls. If we do that we're in deep trouble," Panetta told a news conference in Canada. "We have to operate based on what we believe is the best strategy to achieve the mission that we are embarked on," he said. ...