“The importance of the high north is increasing for NATO and Canada because we are seeing a significant Russian military build-up,” Stoltenberg said, standing next to Canadian Prime Minister Justin Trudeau in Cold Lake, Alberta. Russia has reopened hundreds of Soviet-era military sites in the Arctic, using the area to test new weapons systems, Stoltenberg said. He also warned that Russia and China are forming a strategic Arctic partnership that challenges NATO’s values ​​and interests. Sign up now for FREE unlimited access to Reuters.com Register Canada has been criticized for spending too little on its military capabilities as a member of NATO. But after Russia invaded Ukraine in February, Canada said in June it would invest C$4.9 billion ($3.8 billion) over the next six years to modernize NORAD, the joint North American defense agency U.S.- Canada. “The geopolitical situation has shifted in recent months, so understanding that Russia is a growing concern for all of us makes it timely to share with the Secretary General and with NATO all the things Canada is doing through NORAD.” Trudeau said. Trudeau and Stoltenberg visited Cambridge Bay, Nunavut, on Thursday, a settlement above the Arctic Circle that is home to an air defense radar outpost. It is part of NORAD’s North Warning System, which experts say is in urgent need of upgrades. The more than six-decade-old system detects security threats in North America, and the early warning radar for the polar region dates back to the late 1980s. Both Trudeau and Stoltenberg agreed that climate change is making the Arctic more accessible for economic and military activities, raising security concerns. Cambridge Bay is one of the main stops for ships crossing the Northwest Passage of the Arctic Ocean between the Atlantic and Pacific oceans. The United States has disputed Canada’s sovereignty over the passage for decades, saying it is an international waterway. Asked about the sovereignty issue on Friday, Trudeau said: “The Northwest Passage is Canadian waters. Period.” Sign up now for FREE unlimited access to Reuters.com Register Reporting by Ismail Shakil and Steve Scherer in Ottawa. Edited by Josie Kao Our Standards: The Thomson Reuters Trust Principles.