WASHINGTON (AP) — South Korean President Moon Jae-in’s office says it is trying to figure out President Donald Trump’s intentions in canceling a summit next month with North Korea’s leader.

Moon played a prominent role in planning for the summit with Kim Jong Un, which was scheduled for June 12 in Singapore.

South Korea’s Yonhap News Agency quoted a presidential office spokesman as saying they “are trying to figure out what President Trump’s intention is and the exact meaning of it.”

Trump released a letter to Kim on Thursday saying he had canceled the summit because of “tremendous anger and open hostility” expressed in a recent North Korean statement.

He did not elaborate, but a North Korean vice minister of foreign affairs issued a statement referring to comments by U.S. Vice President Mike Pence as “ignorant” and “stupid,” and saying North Korea is just as ready to meet in a nuclear confrontation as at the negotiating table.