US Secretary of State Rex Tillerson says President Donald Trump has instructed him to continue diplomatic efforts to calm rising tensions with North Korea, saying "those diplomatic efforts will continue until the first bomb drops".
Speaking on CNN's State of the Union, Mr Tillerson downplayed messages that Mr Trump had previously posted on Twitter suggesting Mr Tillerson was wasting his time trying to negotiate with "Little Rocket Man", a derogatory nickname the president has coined for North Korea's leader Kim Jong-un.
Mr Trump "has made it clear to me to continue my diplomatic efforts", Mr Tillerson said.
Mr Tillerson's comments on Sunday come amid soaring tensions between the US and North Korea following a series of weapons tests by Pyongyang and a war of words between the two countries' leaders.
North Korea has conducted a series of nuclear tests in recent weeks and launched two missiles over Japan.
Mr Tillerson has been in talks with China to enlist its help on getting North Korea to back down.
But Mr Trump's recent Twitter messages appeared to undercut Mr Tillerson's efforts, prompting the Senate foreign relations committee chairman Bob Corker to complain that Mr Trump was publicly castrating Mr Tillerson and hurting diplomatic talks.
Mr Tillerson downplayed those tweets on Sunday, telling CNN that Mr Trump and China's President Xi Jinping have an extremely close relationship and that China understands the US position.
"Rest assured that the Chinese are not confused in any way" about the American policy towards North Korea, he added.