( dpa )- The United States will urge NATO allies to send more troops to southern Afghanistan, where most of the fighting with the Taliban and al-Qaeda is taking place, the Pentagon said Tuesday. The reluctance of European NATO allies to contribute more troops to Afghanistan or limit their role to peacekeeping missions has frustrated the United States, and most recently Canada. Canadian Prime Minister Stephen Harper announced Monday that he was extending the mission of his country's 2,500 troops in the country but criticized NATO countries for refusing to send more soldiers. Harper said the extension was contingent on European allies sending more troops to meet requests for an additional 7,000 troops in the heavy fighting area of southern Afghanistan. "The government accepts ... extending Canada's mission in Afghanistan if, and I must emphasize, if certain conditions are met," Harper said. US Defence Secretary Robert Gates has been urging NATO countries to make a greater contribution. He announced earlier this month the deployment of 3,200 Marines to shore up the gap. There are already about 26,000 US soldiers in Afghanistan, about half of them under NATO's command. "At every point along the way we have made it clear that we would like others to step up to the plate as we are," Pentagon spokesman Geoff Morrell said. Germany and France have deployed several thousand troops to Afghanistan, but restrict their use to peacekeeping roles in relatively safe areas of the country, while US, British, Dutch, Danish and Canadian forces take casualties in the fighting against Taliban and al-Qaeda militants in southern Afghanistan. The German government has been considering a NATO request for more troops.