U.S. Defense Secretary Jim Mattis is likely to visit Japan in late June for talks with his Japanese counterpart Itsunori Onodera on North Korea, sources close to bilateral ties said Thursday.

During the talks, which will follow the first-ever U.S.-North Korea summit on June 12, the defense chiefs are expected to reaffirm the two countries' commitment to continuing to apply pressure on North Korea until its complete denuclearization, the sources said.

To underscore the closeness of the allies, U.S. President Donald Trump could also visit Japan to meet with Prime Minister Shinzo Abe after the summit in Singapore with North Korean leader Kim Jong Un.

According to the sources, Mattis' trip to Japan is being arranged at the strong request of the Japanese government. Before visiting Japan, Mattis plans to travel to China for the first time since becoming Pentagon chief in January 2017.

The Japanese government believes close cooperation with the United States is needed more than ever to ensure it is not left behind in the diplomatic developments related to North Korea.

(Mattis and Onodera meet in the Philippines in October 2017.)

Tokyo views the Trump-Kim summit as an opportunity for making progress on the long-stalled issue of Pyongyang's abductions of Japanese nationals decades ago. It also wants the United States to press North Korea to eliminate not only its nuclear weapons but all ballistic missiles, including those that put Japan within range.

Mattis is also likely to meet Onodera in Hawaii later in May when the Pentagon chief is expected to attend a ceremony to mark the change of the commander of the U.S. Pacific Command.

The two defense chiefs are also considering holding bilateral talks on the sidelines of a regional security meeting in Singapore in early June, according to the sources.