North Korean leader Kim Jong-un listens during a meeting with Russia's Foreign Minister Sergei Lavrov in Pyongyang, North Korea, Thursday. / Tass-Yonhap

By Park Ji-won

North Korean leader Kim Jong-un is expanding diplomacy with China and Russia before his summit with U.S. President Donald Trump on June 12.

Kim has met _ or plans to meet _ leaders and high-level officials of China and Russia.

Kim met Russian Foreign Minister Sergey Lavrov in Pyongyang Thursday and agreed to hold a summit with Russian President Vladimir Putin, according to the North's Korean Central News Agency (KCNA), Friday.

"The two countries (North Korea and Russia) agreed to hold a summit as well as boost high-level dialogue, exchanges and cooperation in various fields this year, which marks the 70th anniversary of bilateral diplomatic relations," it said.

The KCNA emphasized denuclearization in the reports, saying Kim told Lavrov the North's will to denuclearize the Korean Peninsula is unchanged, consistent and fixed. Russia's envoy also delivered Putin's letter to Kim, it said.

Critics say the North's engagement with Russia is likely a diplomatic move ahead of the summit with the U.S.

"Through the meeting with the Russian foreign minister, as well as two meetings with Moon, China's Xi Jinping and the U.S.' Pompeo, Kim shows the North's commitment toward denuclearization to the U.S and international society," Yang Moo-jin, a professor at the University of North Korean Studies, was quoted as saying to YTN.

Critics said Russia backs North Korea because it wants to remain part of the summit process.

"Russia de facto supports the North's stance (to take a step-by-step measure to denuclearization) through the foreign minister's remarks that laid out the necessity of lifting sanctions against the North," Cha Doo-hyun, a professor at the University of North Korean Studies, was quoted as saying to YTN.

However, Japan has not been part of the process because the North has refused any talks with its officials.

Japan's Prime Minister Shinzo Abe plans to meet Trump on June 7 before joining the G-7 meeting in Canada beginning June 8. It has taken Abe less than two months to revisit the U.S.

Japan will send its Foreign Minister Kono Taro to Singapore on June 9 to ask for information about the Kim-Trump summit from the Singaporean government, media reports said.