Photo/Illutration In this July 25 photo provided on July 26, by the North Korean government, North Korean leader Kim Jong Un watches a missile test in North Korea. (Korean Central News Agency/Korea News Service via AP)

SEOUL--North Korea on Saturday said leader Kim Jong Un attended a flight demonstration of military aircraft at an airfield on the country’s eastern coast where he instructed combat pilots to acquire “great idea and tactics” against enemies “armed to the teeth.”

The report from Pyongyang’s official Korean Central News Agency followed a slew of statements expressing anger at planned U.S.-South Korea military drills that the North says could derail its nuclear negotiations with Washington.

Currently on a visit to South Korea, U.S. Defense Secretary Mark Esper told reporters on Friday that the allies could possibly modify the joint aerial exercises to create space for diplomacy.

Negotiations have faltered since a February summit between Kim and President Donald 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 has issued an end-of-year deadline for the Trump administration to offer mutually acceptable terms for a deal to salvage the diplomacy while saying that the North would seek a “new path” if the United States persists with sanctions and pressure. The North has been ramping up its missile tests and other military demonstrations in recent months in an apparent attempt to pressure Washington.

KCNA said Kim expressed satisfaction over the performance of his combat pilots who displayed the “invincible might” of his flying corps. The agency didn’t mention any direct comments by Kim toward Washington or Seoul.

Kim said his pilots should be prepared to “fight the enemies armed to the teeth with great idea and tactics under any circumstances,” the agency said.

“He stressed that however loudly the enemies may brag about their technological advantages, they can never overwhelm the politico-ideological and combat and moral advantages of our service personnel,” the agency said.

The report didn’t provide much details on the aircraft deployed for the air show at Wonsan Kalma Airport. It said Kim’s official plane, the “Chammae-1,” named after the goshawk, the North’s national bird, flew over the airfield escorted by other military planes.

A report this week from 38 North, a website specializing in North Korea studies, said commercial satellite images showed tens of military aircraft parked along the airport’s taxiways and parking aprons, including MiG-15, -17 and -29 fighters, II-28 bombers and Su-25 close support aircraft.

Since the start of the nuclear talks last year, the United States and South Korea have canceled or scaled back their regular military drills to create space for diplomacy. But North Korea says the smaller drills are still a rehearsal for an invasion and has reacted strongly to the exercises during stalemates in the negotiations.

On Wednesday, the North’s State Affairs Commission, the country’s supreme decision-making body, lashed out at the planned U.S.-South Korean drills and warned that the that the United States will face a “greater threat” if it ignores Kim’s end-of-year deadline.

After Esper said Washington could alter its military activities with Seoul to accommodate talks with Pyongyang, the North issued another statement saying it would like to consider his remarks as U.S. intention to “drop out of the joint military drill or completely stop it.”

After a meeting with South Korean Defense Minister Jeong Kyeong-doo in Seoul on Friday, Esper told reporters that the allies “remain flexible in terms of how we support our diplomats,” but didn’t specifically comment on the size of the upcoming drills.

“The purpose of our forces and exercises is not only to buttress our diplomacy, but to also enable and empower it," Esper said.