(CBS) — North Korea on Wednesday canceled a high-level meeting with South Korea and also threatened to call off a historic summit next month between President Trump and North Korean leader Kim Jong Un due to ongoing military exercises between the South and the U.S., South Korea’s Yonhap news agency reported. Pyongyang has long claimed those exercises are invasion rehearsals.

The surprise declaration, which came in a pre-dawn dispatch in North Korea’s state media, appears to cool what had been an unusual flurry of outreach from a country that last year conducted a provocative series of weapons tests that had many fearing the region was on the edge of war. It’s still unclear, however, whether the North intends to scuttle all diplomacy or merely wants to gain leverage ahead of the planned June 12 talks between Kim and Trump.

The statement was released hours before the two Koreas were to meet at a border village to discuss setting up talks aimed at reducing military tension along the world’s most heavily armed border and restarting reunions between families separated by the Korean War.

Yonhap says North Korea’s Korean Central News Agency (KCNA) reported that Wednesday’s meeting was canceled and that Pyongyang was questioning whether next month’s summit between North Korea’s Kim Jong Un and President Trumpcan also take place as planned.

“We are aware of the South Korean media report,” White House press secretary Sarah Huckabee Sanders said in response not long after the news broke. “The United States will look at what North Korea has said independently, and continue to coordinate closely with our allies.”

Also Tuesday, State Department spokeswoman Heather Nauert said that the U.S. “will continue to plan the meeting between President Trump and Kim Jong Un.”

“The United States must carefully contemplate the fate of the planned North Korea-U.S. summit amid the provocative military ruckus that it’s causing with South Korean authorities,” KCNA reported.

The Pentagon says the military exercise is a routine, annual event that is purely defensive in nature. Army Col. Rob Manning says Exercise Max Thunder 2018 is designed to improve the abilities of the U.S. and South Korea to operate together. It began Monday and is slated to run through May 25, and is expected to include aircraft from the U.S. Air Force, Army, Navy and Marine Corps, as it has in the past.

“The defensive nature of these combined exercises has been clear for many decades and has not changed,” said Manning.

Last year it included as many as 1,200 U.S. personnel and about 640 South Koreans as well as various aircraft including F-16 fighter jets, F-18 Hornets and EA-18G Growlers from the Navy’s electronic attack squadron. Manning says the defensive nature of these combined exercises has been clear for many decades and has not changed.

Annual military drills between Washington and Seoul have long been a major source of contention between the Koreas, and analysts have wondered whether their continuation would hurt the detente that, since an outreach by Kim in January, has replaced the insults and threats of war. Earlier — and much larger — springtime drills, which Washington and Seoul toned down, went off without the North’s typically fiery condemnation or accompanying weapons tests.

In March, then-CIA Director and current Secretary of State Mike Pompeo told “Face the Nation” that Kim has allowed the U.S. to “continue our exercises on the peninsula something that’s been fought over for decades.” He also made similar remarks the same day on Fox News, saying Kim has “got to continue to allow us to perform our militarily necessary exercises on the peninsula and then he’s got to make sure that he leaves on the table that discussion for denuclearization.”

In March, South Korean National Security Adviser Chung Eui-Yong said Kim “understands that the routine joint military exercises between the Republic of Korea and the United States must continue” after meeting with Mr. Trump at the White House.

Washington and Seoul delayed an earlier round of drills in the spring because of the North-South diplomacy surrounding February’s Pyeongchang Winter Olympics in the South, which saw Kim send his sister to the opening ceremonies.

South Korea didn’t immediately make any official response to the North’s announcement.

The North’s statement Wednesday comes amid a flurry surprising moves from the North in recent weeks.

On Tuesday, South Korea’s military said North Korea was moving ahead with plans to close its nuclear test site next week, an assessment backed by U.S. researchers who say satellite images show the North has begun dismantling facilities at the site.

The site’s closure was set to come before the Kim-Trump summit, which had been shaping up as a crucial moment in the decades-long push to resolve the nuclear standoff with the North, which is closing in on the ability to viably target the mainland United States with its long-range nuclear-armed missiles.

Despite the North’s moves, some experts were skeptical about whether Kim would completely give up a nuclear program that he had pushed so hard to build. Kim has expressed his intention to negotiate over his weapons, but he still uses a long-contentious term, “the denuclearization of the Korean Peninsula.” The North previously has used this phrase when demanding that the United States pull its 28,500 troops out of South Korea and withdraw its so-called “nuclear umbrella” security guarantee to South Korea and Japan as a condition for its nuclear disarmament.

Wednesday’s threat could also be targeted at showing a domestic audience that Kim is willing to stand up to Washington. Kim has repeatedly told his people that his nukes are a “powerful treasured sword” that can smash U.S. hostility.

North Korea also has a long history of launching provocations or scrapping deals with Seoul and Washington at the last minute.

In 2013, North Korea abruptly cancelled reunions for families separated by the 1950-53 Korean War just days before they were held to protest what it called rising animosities ahead of joint drills between Seoul and Washington. A year earlier in 2012, the North conducted a prohibited long-range rocket launch weeks after it agreed to suspend weapons tests in return for food assistances.

CBS News’ Kylie Atwood and Steven Portnoy contributed to this report.