I think Tillerson is simply making sure that NK and the rest of the world know we’re ready to talk, but some things must precede any discussions. Then when Rocket Boy again ignores us, that we have shown the world that negotiations are impossible, paving the way for a preemptive strike if NK doesn’t stop all launching and testing.
Then there’s this business of the “refugee preparations” just across the Yalu River in China. I think China knows where this is going already.
Best (improbable) case is that China has operatives close to Rocket Man getting ready to solve the problem in a singular and personal sort of way.
Realistically, it would appear that they're getting ready to manage refugees,