South Korean President Moon Jae-in and his U.S. counterpart Donald Trump on Sunday pledged to work closely to ensure the success of the planned Trump-Kim summit in a phone conversation.

In this March 27, 2018 photo, a man watches a TV screen showing file footages of U.S. President Donald Trump, right, South Korean President Moon Jae-in, center, and North Korean leader Kim Jong Un, left, during a news program at the Seoul Railway Station in Seoul, South Korea. File Photo: AP/Lee Jin-man

The two leaders have exchanged their point of views on the recent responses from the Democratic People's Republic of Korea (DPRK) when they held talks via telephone for 20 minutes, according to Cheong Wa Dae, South Korea's presiential office.

Both leaders have decided to work closely and unswervingly for the successful U.S.-DPRK summit slated on June 12, as well as the upcoming meeting between Moon and Trump, said the office.

Moon is scheduled to visit Washington next week to hold a meeting with President Trump in a bid to help the upcoming summit between the DPRK and the United States become a success. 

The Moon-Trump summit is anticipated to serve as a bridge to lead to a successful DPRK-U.S. summit, the presidential National Security Office said on Friday.

On Wednesday, Pyongyang said it may reconsider the scheduled U.S.-DPR Ksummit because of extremely provocative remarks made by American officials. 

Kim Kye Gwan, the DPRK first vice foreign minister said in a statement that the Trump administration must show sincerity in its desire to meet with the DPRK to improve bilateral relations.

Before the statement, the DPRK threatened earlier in the day to withdraw from the scheduled meeting with the United States on June 12 due to on-going U.S.-South Korea joint war games, which kicked off on May 11.

Chinese Foreign Ministry spokesperson Lu Kang said Friday that China will continue to encourage the United States and the DPRK to build mutual trust, and make joint efforts to promote the political resolution of the Korean Peninsula issue.

Kim and Trump are scheduled to meet in Singapore on June 12 for the first-ever DPRK-U.S. summit.