Secretary of State Rex Tillerson said the U.S. expects North Korea to be in direct touch after President Donald Trump agreed to Kim Jong Un's invitation to meet, urging patience as preparations for the potentially historic handshake are worked out.

"We've not heard anything directly back from North Korea, although we expect to hear something directly from them," Tillerson said in Abuja, Nigeria, in response to a reporter's question about the timing and location of the meeting. "I know those are all questions that people are anxious to have answers to. I would say just remain patient and we'll see what happens."

Tillerson's remarks that these things take time contrast with Trump's on-the-spot acceptance of Kim's invitation when South Korea's national security adviser informed him about it at the White House last week. Trump dispensed with decades of U.S. foreign policy orthodoxy with his decision, particularly given that the North Korean leader made only a vague offer — conveyed via a South Korean delegation that visited him — to discuss giving up his nuclear weapons program.