BRUSSELS: The United States (US) military is not ready yet for Russian cooperation, Pentagon Chief James Mattis said on Thursday after Moscow;s defence minister called for better ties. “We are not in a position right now to collaborate on a military level, but our political leaders will engage and try to find common ground or a way forward,”Mattis told reporters at a NATO summit in Brussels. Russian Defence Minister Sergei Shoigu had earlier said that Moscow is ready to restore cooperation with the Pentagon.