North Korea’s decision on Wednesday to suspend ministerial-level inter-Korean meeting is regrettable and is not in line with a historic declaration announced between the two Koreas in late April, South Korea’s unification ministry said.

A ministry spokesperson told reporters that Pyongyang’s decision to unilaterally postpone high-level talks between the two Koreas citing an annual joint air drill between South Korea and the United States, was not in line with the spirit of the Panmunjom Declaration and was regrettable.

Unification Ministry spokesperson Baik Tae-hyun urged the North to swiftly return to the talks.

An official statement would be sent to North Korea some time on Wednesday, he said.

Earlier North Korea said it was suspending high-level talks with South Korea scheduled for later in the day on Wednesday (May 16) due to U.S.-South Korean military exercises that it said went against the trend of warming North-South ties.

North Korea’s official Korean Central News Agency (KCNA) also cast doubt on whether next month’s summit between North Korean leader Kim Jong-un and U.S. President Donald Trump could go ahead as planned.

Wednesday’s meeting was due to focus on plans to implement a declaration that emerged from an April 27 inter-Korea summit in the border village of Panmunjom, including promises to formally end the Korean War and pursue “complete denuclearization,” the South’s unification ministry, which handles ties with the North, said on Tuesday.

KCNA called the U.S.-South Korean “Max Thunder” air combat drills, which it said involved U.S. stealth fighters and B-52 bombers, a “provocation” and said Pyongyang had no choice but to suspend the talks.