The following is a chronology of major developments leading to Tuesday's announcement of a second summit between U.S. President Donald Trump and North Korean leader Kim Jong-un.

Feb. 25, 2018 -- Kim Yong-chol, a close aide to the North Korean leader, expresses an openness to talks with the United States in a meeting with South Korean President Moon Jae-in, while visiting the South for the closing ceremony of the PyeongChang Winter Olympic Games.

March 8, 2018 -- Chung Eui-yong, South Korea's presidential national security adviser, announces after a meeting with Trump at the White House that the U.S. president has agreed to meet Kim in May.

March 25-28, 2018 -- Kim makes his first visit to China since assuming power and meets with Chinese President Xi Jinping.

March 31-April 1, 2018 -- U.S. Central Intelligence Agency Director Mike Pompeo visits Pyongyang and meets with Kim to lay the groundwork for the first Trump-Kim summit.

April 27, 2018 -- Moon holds his first summit with Kim at the inter-Korean border village of Panmunjom.

May 9-10, 2018 -- Pompeo, now the U.S. secretary of state, makes his second trip to North Korea to discuss denuclearization and bring home three Korean-American detainees released by Pyongyang.

May 10, 2018 -- Trump announces on Twitter that the first-ever U.S.-North Korea summit will be held in Singapore June 12.

May 22, 2018 -- Moon and Trump hold talks in Washington.

May 24, 2018 -- North Korea demolishes its nuclear testing site in Punggye-ri in front of a group of international reporters.