WASHINGTON - Secretary of State Rex Tillerson said Sunday that President Donald Trump had 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," Tillerson downplayed messages that President Trump had previously posted on Twitter suggesting Tillerson was wasting his time trying to negotiate with "Little Rocket Man," a derogatory nickname Trump has coined for North Korea's leader Kim Jong Un.Trump "has made it clear to me to continue my diplomatic efforts," Tillerson said.