The spokeswoman said that there has been no change in Washington's policy, which is maximum pressure against North Korea and the denuclearization of the Korean Peninsula.
"However, if there is dialogue between the United States and North Korea, there could be some sort of compromise", the expert said, adding that he is cautious but optimistic about such dialogue.
Moon met Kim in Pyeongchang, where the Olympics were held, before the closing ceremony, the South Korean government said.
Conservative lawmakers staged an overnight protest near the border with the North, joined by hundreds of other activists, forcing Kim's motorcade to take an alternate route.
After the Paralympics end in March, South Korea and the U.S. are due to hold delayed large-scale joint military exercises which always infuriate Pyongyang. "The U.S. will have to pay dearly for stupid and wild vituperation".
While its athletes are returning home empty-handed from the Winter Olympics, analysts say nuclear-armed North Korea deserves a gold medal for its diplomatic skills - but that the Games-driven detente will be short-lived.
North Korea has not fired any missiles since November a year ago but it defends the weapons programmes as essential to deter U.S. aggression.
North Korea has condemned the new sanctions and accused Washington of trying to undermine the improvement in inter-Korean relations.
Kim led an eight-member North Korean delegation to the ceremony, in the latest sign that the two Koreas were working toward a political detente after years of rising tensions over the North's nuclear weapons program.
"There is a need for the United States to lower the threshold for talks with North Korea, and North Korea should show it is willing to denuclearize".
Their lunch was in the Chinese restaurant at the relatively isolated Walker Hill hotel, where the North Korean leader's sister stayed during her visit earlier this month and where the current delegation is staying.
Despite the divisions and distrust between the two Koreas, they agreed to have their athletes march together at both the opening and closing ceremonies under a banner of unification.
Their agreement on athletes will be reviewed by the International Paralympic Committee for approval. Ivanka Trump, who was leading the US delegation, briefed Moon on the latest set of sanctions and delivered a personal message from her father after she arrived in Seoul on Friday for her four-day visit.
Ivanka, meanwhile, was planning to meet North Korean defectors during her trip to South Korea as she showed interest in the issue, but the meeting was said to be canceled.
And Gaffney finds the South Korean president's pandering at the Olympics disturbing.
She was the center of a frenzy of attention, especially when she appeared at the opening ceremony and was only a few feet from U.S. Vice President Mike Pence.
U.S. President Donald Trump responded to North Korea's overture by saying that talks with North Korea will happen only if conditions are right.