Russia on Thursday sharply raised the stakes in its dispute with the West over Ukraine, with a top diplomat refusing to rule out a Russian military deployment to Cuba and Venezuela if tensions with the United States mount. Deputy Foreign Minister Sergei Ryabkov, who led the Russian delegation in Monday’s talks with the U.S. in Geneva, said he could “neither confirm nor exclude” the possibility of Russia sending military assets to Cuba and Venezuela if the talks fail and U.S. pressure on Russia mounts. The Russia-U.S. negotiations in Geneva and a subsequent NATO-Russia meeting failed to narrow the gap on...