WASHINGTON (Reuters) - China has told the United States that it warned Pyongyang it would impose “sanctions actions on their own” against North Korea should it carry out another nuclear test, U.S. Secretary of State Rex Tillerson said on Thursday. Tillerson, speaking on Fox News, also said U.S. intelligence reports suggest that North Korean leader Kim Jong Un was “not crazy,” indicating he might be a rational actor who could be negotiated with as the international community seeks to rein in Pyongyang’s nuclear and missile programs. Tillerson’s comments suggest that efforts by President Donald Trump, who held a summit with Chinese President Xi Jinping earlier this month, may have yielded China’s toughest threat yet to take action against its defiant neighbor and ally, North Korea. 