North Korea on Saturday threatened the United States with “miserable destruction” if the Pentagon goes ahead with its annual, routine military exercises with South Korea next month.

“You had better bear in mind that those igniting a war are destined to meet a miserable destruction,” said Pak Rim Su, chief of North Korea’s military delegation to the Demilitarized Zone between the two countries.

He called the drills were “reckless,” accusing the United States and South Korea of preparing to invade the north.

The regularly scheduled joint drills come amid heightened tensions, as North Korea last week confirmed that it had conducted its most powerful nuclear test to date, in a striking act of defiance that drew condemnations from around the globe.

The nuclear test follows previous detonations by the North in 2006 and 2009. The latest bomb tested had greater explosive force and utilized a smaller, lighter device, the North’s state-run Korean Central News Agency (KCNA) reported last week.

U.S. President Barack Obama has vowed to pursue further sanctions against North Korea following the tests.

“We have had close consultations on a wide range of security issues, in particular our concerns about the provocative actions that have been taken in North Korea and our determination to take strong actions in response,” Obama said Friday.