washington u.s. republican senator bob corker step public feud donald trump friday say u.s. president undermine top diplomat like castrate public corker tell washington post interview trump undercut secretary state rex tillerson efforts enlist china rein north korea nuclear program denigrate diplomat publicly castrate secretary state without limit options deal north korea corker chairman senate foreign relations committee tell post tillerson tell news conference beijing two weeks ago unite state directly communicate north korea nuclear missile program show interest dialogue trump take twitter next day say tillerson waste time try negotiate north korean leader kim jong un great diplomatic activities china important come long long way corker say things talk phenomenal jack legs chief diplomat cause fall apart corker tell post add work china key reach peaceful settlement north korea publicly castrate secretary state take table republican senator corker blast trump 'castrating tillerson