North Korean leader Kim Jong Un supervised a parachuting drill of military sharpshooters and vowed to build an “invincible army,” displaying more defiance even as the United States and South Korea called off their own exercises to create space for nuclear diplomacy, Eurasia Diary reports citing Associated Press.

The report Monday by the Korean Central News Agency came hours after President Donald Trump in a tweet urged Kim to “act quickly, get the deal done” while hinting at another summit, writing, “See you soon!”

At an Asian defense ministers’ conference in Bangkok on Sunday, U.S. Defense Secretary Mark Esper said the United States has indefinitely postponed a joint military exercise with South Korea in an “act of goodwill” toward North Korea. Diplomats have been pushing to resume stalled nuclear talks ahead of Kim’s end-of-year deadline for the Trump administration to salvage the diplomacy.

North Korea has publicized two military drill in three days. A report Saturday said Kim urged combat pilots to prepare against enemies “armed to the teeth” while attending a flight demonstration.

KCNA published photos that showed Kim posing with North Korean air force sharpshooters and soldiers who used white parachutes to land on a training field.

Kim while supervising the drill said it’s “necessary to wage a drill without notice under the simulated conditions of real war” for improving his military’s war readiness and build it into an “invincible army,” KNCA said. Kim did not make any specific comment toward Washington or Seoul in the report.

North Korea has been ramping up missile tests and other military demonstrations in recent months in an apparent pressure tactic over the talks.

Negotiations have faltered since a February summit between Kim and Trump in Vietnam, which broke down after the U.S. rejected North Korean demands for broad sanctions relief in exchange for a partial surrender of its nuclear capabilities.

Kim issued an end-of-year deadline for the Trump administration to offer mutually acceptable terms for a deal while saying that the North would seek a “new path” if the United States persists with sanctions and pressure.

Working-level talks last month in Sweden broke down over what the North Koreans described as the Americans’ “old stance and attitude.”

North Korea last week said the United States has proposed a resumption of stalled nuclear negotiations in December. But North Korean negotiator Kim Myong Gil didn’t clearly say whether the North would accept the supposed U.S. offer and said the country has no interest in talks if they are aimed at buying time without discussing solutions.

He said the North isn’t willing to make a deal over “matters of secondary importance,” such as possible U.S. offers to formally declare an end to the 1950-53 Korean War, which was halted by a cease-fire, not a peace treaty, or establish a liaison office between the countries.