South Korean President Moon Jae-in, on a mission to Washington on Thursday to kick-start nuclear diplomacy by persuading U.S. President Donald Trump to ease crushing sanctions on North Korea and gain an OK for inter-Korean projects, fell short in talks with Trump.

But is there a path forward for the U.S. and North Korea? And if so, what role could Moon play?

Trump rejected Moon's calls for planned confidence-building economic projects with Pyongyang, dealing a blow to his efforts to restart nuclear talks with Kim Jong Un after Trump's summit with the North Korean leader broke down in Hanoi in late February, in part over Kim's demands for immediate sanctions relief.