WASHINGTON (Reuters) - U.S. President George W. Bush warned on Wednesday a nuclear-armed Iran could lead to World War III as he tried to shore up international opposition to Tehran amid Russian skepticism over its nuclear ambitions. Bush was speaking a day after Russian President Vladimir Putin, who has resisted Western pressure to toughen his stance over Iran's nuclear program, made clear on a visit to Tehran that Russia would not accept any military action against Iran. At a White House news conference, Bush expressed hope Putin would brief him on his talks in Tehran and said he would ask...