Sweden will sign a contract to buy the Patriot air defense missile system from US arms manufacturer Raytheon Co this week, Swedish radio reported on Wednesday. Sweden is not a North Atlantic Treaty Organization (NATO) member. However, it has close ties to the alliance and has been beefing up its armed forces, Reuters said. Sweden’s existing air defense system cannot shoot down ballistic missiles. Stockholm will buy four Patriot firing units and an undisclosed number of missiles, according to the report. “There are a number of other countries that already have it and we expect the first delivery in 2021,”Swedish radio quoted Defense Minister Peter Hultqvist saying.