New South Korean President Moon Jae-in will visit the White House next month for a summit with President Donald Trump amid worries over North Korea’s progress in building a nuclear and missile arsenal, Seoul’s presidential office said Tuesday.

The agreement for the leaders to meet in late June followed a meeting in Seoul between Chung Eui-yong, Moon’s foreign policy adviser, and Matt Pottinger, the Asia director on Trump’s National Security Council, Moon’s spokesman Yoon Young-chan said.

The announcement came days after North Korea successfully tested a powerful new missile that analysts believe could reach Alaska when perfected.

Under the leadership of third-generation dictator Kim Jong Un, North Korea has been speeding up its pursuit of a decades-long goal of developing nuclear-armed missiles capable of reaching the U.S. mainland.

North Korea conducted two nuclear tests last year which are likely to have improved its know-how in making nuclear weapons small enough to fit on long-range missiles. Experts say the “medium long-range” Hwasong-12 missile the North fired on Sunday achieved a higher altitude and longer flight time than any other missile the country has tested.

Also Tuesday, Adm. Harry Harris Jr., the top American military officer in the Pacific, met with Japanese Prime Minister Shinzo Abe in Tokyo to discuss the North Korean missile launch. They said the North’s “unacceptable” action underscored the importance of the U.S.-Japan alliance.

“We now need to apply pressure on North Korea, and Japan and the United States need to coordinate closely so as to apply pressure,” Abe told reporters.

Yoon said Chung and Pottinger in their meeting reaffirmed that Seoul and Washington share a common goal in the “complete discarding” of North Korean nuclear weapons and will pursue “all methods, including sanctions and dialogue” to reach the goal. The allies agreed that dialogue with North Korea could happen under the “right conditions,” Yoon said.

“There was a basic exchange of opinions about North Korea’s nuclear and missile provocations,” Yoon said about the meeting between Chung and Pottinger. “The United States reconfirmed its firm commitment to defend South Korea and both sides also agreed to strengthen collaborative efforts to deter North Korean provocations.”

A date and other specifics of the summit are still to be decided, Yoon said. He said the countries will prepare for the summit so that it “serves as an opportunity for both leaders to develop their personal bond and friendship.” Pottinger later told reporters that the countries reaffirmed “desires to get the two leaders together quickly” following a telephone conversation last week that Trump used to invite Moon to the White House.

“The state of the alliance is strong and I am fully confident that it will only grow stronger between our two administrations,” Pottinger said.

Moon, a liberal, favors a softer approach to North Korea than his conservative predecessors and has offered to visit Pyongyang if the circumstances are right. He has shown a willingness to challenge the United States, saying that Seoul should reconsider its deployment of an advanced U.S. missile defense system to better cope with North Korean threats. However, Washington remains Seoul’s closest ally and military protector.

Moon took office last week after winning an election triggered by the ouster of his conservative predecessor, Park Geun-hye, who was removed from office and jailed in March over corruption allegations. Moon has criticized Park’s hard line against the North, saying the approach did nothing to prevent the North from expanding its nuclear weapons and missiles arsenal and only reduced Seoul’s voice in international efforts to deal with its rival.

(AP)