Russia and Belarus will strengthen military cooperation with a deal to form a joint air defense system, the Russian president said Tuesday. The deal will likely be signed Tuesday, after President Dmitry Medvedev and his Belarusian counterpart, Alexander Lukashenko, hold talks in the Kremlin. The air defense deal "will significantly increase the defense capability of Russia and Belarus," Medvedev said at the start of the talks. Russia has backed Belarus with cheap energy supplies and loans, and former Soviet neighbors have a union agreement that envisages close political and economic ties. Both countries mistrust Western intentions, and have denounced NATO's expansion into former Soviet turf and U.S. plans to build missile defense sites in Poland and the Czech Republic.