Meanwhile, South Korean President Moon Jae-in spoke on the phone Saturday morning with President Trump for about 30 minutes, and they agreed that dialogue with North Korea should continue.
Here's the announcement yesterday at the Blue House.
"The two leaders agreed that the recent situation on the Korean Peninsula is grave, and they acknowledged the need to maintain the momentum for successful dialogue on denuclearization negotiations between North Korea and the U.S."
The Blue House says the talks were held at President Trump's request, and the two leaders agreed to talk whenever necessary.
A senior official at the top office said it's difficult to reveal what kind of detailed measures were discussed.
But the official said the leaders did not discuss other issues like defense cost-sharing for American troops in Korea or the military intel-sharing pact with Japan.