North Korean leader Kim Jong Un. Reuters When the White House announced new South Korean President Moon Jae-in’s visit to Washington, D.C. earlier this month, it described the alliance between the United States and the Republic of Korea as "ironclad."

But as Moon’s visit, scheduled for Thursday and Friday, draws closer, one thing to watch will be the relationship between the Korean leader, who campaigned on a platform of more engagement with Pyongyang, and his American counterpart, who has pushed a hawkish line on North Korea since he took office.

North Korea, obviously, will dominate the visit, a senior White House official said in a call with reporters on Wednesday, stressing that the two would discuss "coordinating" their approach to dealing with Pyongyang. The official also said that the two countries share the goal of "complete dismantlement" of North Korea’s nuclear program.

Also sure to come up: A new US missile defense system recently deployed to South Korea, which Moon has suspended on environmental grounds. While the White House official said "South Korea in many respects is the model ally" in terms of defense spending, Trump himself said as recently as April that South Korea should pay for the billion dollar THAAD system.

But the real real test will be how the two leaders deal with North Korea. The left-leaning Moon, elected in May after his predecessor, the conservative Park Geun-hye, was ousted for corruption, has long been an advocate for dialogue with North Korea. Moon was chief of staff to then-President Roh Moo-hyun from 2003 to 2008, which means he was part of an administration that actively pursued "sunshine policies" — that is, policies of greater political and economic engagement with the North. A Terminal High Altitude Area Defense (THAAD) interceptor. Thomson Reuters

Moon has changed his tune a bit since taking office, talking tougher than he had been in response to North Korean dictator Kim Jong Un’s bad behavior, notes Michael Mazza of the American Enterprise Institute, though he still calls Moon a "pro-engagement kind of guy."

The White House, for its part, made clear that it wants a unified front to pursue engagement only when the conditions are right. And even then, "we must maintain and increase pressure in North Korea."

Also on the agenda: Trade. There will be a "friendly and frank discussion about the trade relationship," the administration official said. Trump will likely look to pave a path toward the renegotiation of the US free trade deal with South Korea, which he described in April as "unacceptable."

The South Korean Embassy in Washington did not immediately respond to a request for comment regarding their expectations for the trip, which will include a visit to the Korean War Memorial and lunch with Vice President Mike Pence.