Why?
Where’s the breaker bar to ratchet the sanctions tighter?
Because they'd been through many preliminaries and scheduled a meeting with the possibility of ending a dangerous standoff that has been around since the 1950s. It is pointless to continue joint US/SK military maneuvers two or three weeks before an historic meeting and opporunity.
There comes a times to stop chest beating and muscle flexing. If the negotiations fail, there is all of the future to go back to the old ways in Korea.
The military maneuvers should be doubled in size and duration. Increase the pressure on the crazy commie.