"The World is watching", Trump warns Iran leaders about protesters

US President Donald Trump warned Iran Sunday against killing protesters who have risen up over the regime's downing of a civilian airliner as his defense secretary left the door open to talks with Tehran without preconditions. Trump's salvo came as Iran's Islamic regime faced a challenge from angry street protests, having come to the brink of war with the US after a series of tit-for-tat confrontations.