U.S. President Donald Trump called Sunday on North Korean leader Kim Jong Un to hold a summit "soon," as denuclearization negotiations between the two nations have shown few signs of moving forward.

Pyongyang quickly responded to Trump's remarks on Monday, urging the United States to abandon its "hostile policy" against North Korea if it wants to continue bilateral talks.

Earlier Monday, meanwhile, North Korean First Vice Foreign Minister Choe Son Hui, a close aide to Kim, left Pyongyang for Russia, apparently to exchange views with Russian officials on how to expedite negotiations with the United States.

As North Korea has asked the United States to shift what Kim has claimed are one-sided demands in nuclear talks by the end of this year, all eyes are on whether the two countries can resume their stalled working-level meeting in the not-so-distant future.

Addressing Kim directly, Trump tweeted on Sunday, "I am the only one who can get you where you have to be. You should act quickly, get the deal done. See you soon!"

On the same day, the United States and South Korea said that they have decided to postpone their joint air defense exercises, scheduled for later this month, as an olive branch to the North. Pyongyang has denounced such drills as rehearsals for an invasion.

But Kim Kye Gwan, adviser to the North Korean Foreign Ministry, said in a statement carried by the official Korean Central News Agency that ties between the two nations have not improved much even though Kim Jong Un and Trump have met three times since June last year.

North Korea is "not interested" in a "fruitless" summit, Kim Kye Gwan, a former chief nuclear negotiator with the United States, said, adding, "If the United States really does not want to let go of the thread of dialogue, it should make a decision to withdraw its hostile policy."

Ensuring the continuation of the political system led by Kim Jong Un is believed to be the primary goal of North Korea.

Washington and Pyongyang held a working-level meeting in Stockholm in early October, but it ended without progress. Kim Myong Gil, who has also led the negotiations for the North, said the talks broke down as Washington came to the table "empty-handed."

At the first-ever U.S.-North Korea summit in June 2018 in Singapore, Trump promised to provide security guarantees to Pyongyang in return for "complete" denuclearization of the Korean Peninsula.

North Korea, however, has argued that the United States has not implemented the agreement despite Pyongyang taking what it says are concrete steps to discard nuclear weapons.

In recent months, North Korea has continued to test its weapons technology. It has warned it may restart nuclear and intercontinental ballistic missile tests if negotiations with the United States fail to achieve a breakthrough by the end of this year.

The United States and North Korea technically remain in a state of war after the 1950-1953 Korean War ended in a cease-fire. The two countries have no diplomatic relations.