By Trevor Hunnicutt and Dmitry Antonov WASHINGTON/MOSCOW (Reuters) – U.S. President Joe Biden told Russia’s Vladimir Putin on Saturday that the West would respond decisively to any invasion of Ukraine, adding such a step would produce widespread suffering and isolate Moscow. In the latest effort to manage growing hostility, the two men spoke by phone for an hour a day after Washington and its allies warned that the Russian military, which has 100,000 troops massed near Ukraine, could invade at any moment. Moscow has dismissed those warnings as “hysteria.” Neither side said there had been any b…