"The situation on the Korean peninsula and the region is now at a standstill and has reached a critical point where it may return to its original state as the U.S. took a unilateral attitude in bad faith at the recent second DPRK-US summit talks," Kim was quoted as saying by the KCNA.

"And (he) added that peace and security on the Korean peninsula will entirely depend on the U.S. future attitude, and the DPRK will gird itself for every possible situation," it said, using the initialism of the North's official name, the Democratic People's Republic of Korea.

Nuclear negotiations have been stalled after the second summit between Kim and Trump in late February ended without an agreement due to differences over Pyongyang's denuclearization steps and Washington's sanctions relief.

In his recent policy speech at the Supreme People's Assembly, Kim expressed a willingness to hold a third summit with Trump but urged Washington to come up with a "fair" and "mutually acceptable" deal. Kim suggested the end of the year as a deadline for the US to come up with a new proposal acceptable to Pyongyang.

Since the no-deal summit, North Korea has been intensifying diplomacy with its neighboring countries, including Russia, in an apparent bid to enlist their support ahead of its future nuclear negotiations with the US.

In the Vladivostok meeting, Kim and Putin discussed denuclearization and bilateral relations. Putin, in particular, called for the peaceful resolution of Pyongyang's nuclear problem, stressing the need for an "international" security guarantee for the North, which analysts say might signal Russia's desire to play a larger role on Korean Peninsula issues.

In Washington, the State Department said the US will continue to work with the international community to achieve North Korea's denuclearization, avoiding direct comment on the summit between Kim and Putin.

"We will continue to closely coordinate with allies and partners on achieving the world's shared goal of the final, fully verified denuclearization of North Korea," a State Department spokesperson told Yonhap News Agency on Thursday (local time) when asked how the US views the summit."

The KCNA reported that the two leaders "agreed to more closely promote mutual understanding and bonds, and boost strategic collaboration for ensuring regional peace and security in the future."

They also agreed to take "positive measures" in various fields in order to further energize their cooperation in trade, economy, science and technology, while putting the "equally beneficial economic and trade relations between the two countries on a higher stage."

Kim invited Putin to visit North Korea "at a convenient time," and the Russian leader accepted the invitation, the KCNA said.

This week's summit was the first meeting between the leaders of the two countries in eight years, after Kim's late father, former leader Kim Jong-il, met then Russian President Dmitry Medvedev in 2011.

The KCNA did not provide details on until when Kim will stay in Russia. Russia's TASS news agency said the North Korean leader will leave Vladivostok later Friday. (Yonhap)