Putin says U.S. missile systems in Alaska, South Korea challenge Russia

By Denis Pinchuk and Andrew OsbornST PETERSBURG/MOSCOW (Reuters) - Russian President Vladimir Putin said on Thursday that elements of a U.S. anti-missile system in Alaska and South Korea were a challenge to Russia and that Moscow had no choice but to build up its own forces in response.Putin, speaking at an economic forum in St Petersburg, said Russia could not stand idly by and watch while others increased their military capabilities along its borders in the Far East in the same way as he said