Both scenarios are part of an accelerated review of North Korea policy prepared in advance of Trump's meeting with Chinese President Xi Jinping this week.

The White House hopes the Chinese will do more to influence Pyongyang through diplomacy and enhanced sanctions. But if that fails, and North Korea continues its development of nuclear weapons, there are other options on the table that would significantly alter U.S. policy.

The first and most controversial course of action under consideration is placing U.S. nuclear weapons in South Korea. The U.S. withdrew all nuclear weapons from South Korea 25 years ago. Bringing back bombs — likely to Osan Air Base, less than 50 miles south of the capital of Seoul — would mark the first overseas nuclear deployment since the end of the Cold War, an unquestionably provocative move.