The official was referring to Seoul's decision to suspend the deployment of an additional four THAAD launchers pending an environmental assessment. South Korea has rejected speculation the halt might be a precursor to reversing the decision on THAAD deployment altogether.

The White House official said that Trump wants to have frank discussions on trade.

"His view is that there are aspects of the trade relationship that aren't in balance. He will be, I think, forthright in talking about things like US autos and the fact that there are still some barriers to US auto sales in Korea; certainly, the enormous amount of steel that sometimes ends up being surplus Chinese steel that comes to the United States via South Korea," the official said.

Though South Korea's trade surplus with the US is shrinking and US exports rising, there is still a "large gap," the official said.

"It's caught the president's eye. And I think that he'll talk about that," he said.

On North Korea, the official said that the US wants to stay closely coordinated with the South, adding that it doesn't matter that Moon's government is from a different political party than the previous government.

"The similarities in our approaches are already evident. I mean, if we look at what President Moon has said to date, both in terms of the overarching goal of denuclearization. He made a comment the other day about, you know, the engagement that he would eventually seek with North Korea, being very similar to what President Trump has talked about," he said.

"And that is engagement when the conditions are right. And until they are right, and even once the conditions may present themselves to enter into dialogue, we must maintain and actually increase pressure on North Korea. That's President Moon's approach. It's President Trump's approach. So, we're actually quite comfortable with where the two governments are right now," he said.

Trump's policy is to substantially increase economic and diplomatic pressure on the North in order to change its calculus to have substantive talks once it shows they're willing to begin reducing the threat, the official said.

"Right now, we see no evidence that they are seeking to reduce the threat, in the form of nuclear weapons, in the form of missile -- ballistic missile technology, including work being conducted on an ICBM capability that's clearly designed -- explicitly designed to threaten Americans here at home," he said.

The official also called for China to do more to pressure the North.

"China is still falling far short of what it could bring to bear on North Korea in terms of pressure," he said. "The salient point here is that we very much want to see China do more than -- than it's willing to do. While we do recognize that China's doing more than it has done in the past.

The official praised South Korea as a "model ally" in terms of defense cost sharing.

"South Korea, in many respects, is the model ally because they are spending somewhere on the order of 2.7 percent of their GDP on their defense," he said. "South Korea has paid an enormous amount of money to help host US troops in their country, including through things like -- is it Camp Humphreys? -- the new base south of Seoul, which 92 percent of that cost was shouldered by South Korea."

Burden-sharing is part of the conversation Trump has with allies, but the US "shouldn't view South Korea as somehow laggard on that front," the official said. He also said that he doesn't sense that there's "any significant trouble on that front." (Yonhap)