The reason we can't attack the Norms is because they would immediately destroy Seoul.
Any attempts to evacuate Seoul in preparation of an attack would tip off the Norms.
What will we Do?
Force an evacuation through the guise of a natural disaster.
Seoul is very prone to natural disasters. Tsunamis, harsh winters and landslides pose a great risk.
The Administration is just waiting for an excuse to evacuate Seoul to strike first. Expect movement as soon as any natural occurrence can be blamed for fast evacuations. The UN will be sent in for evacuations along with US soldiers prepared for a ground invasion as soon as major sites are bombed.
This will be considered the first historic use of weather warfare.