North Korea threatened to unleash a powerful action if the U.S. does not halt joint military drills with partners including South Korea, in what might be an effort by Kim Jong Un to lay the groundwork for his first nuclear test in five years.

“If the U.S. continuously persists in the grave military provocations, the DPRK will take into account more powerful follow-up measures,” the state’s foreign ministry said in a statement released on official media Tuesday. Such ministry statements are often used by the country, officially known as the Democratic People’s Republic of Korea, to make clear the warning is coming from Kim’s regime.

The U.S. and South Korea this week started joint air drills known as Vigilant Storm that will run through Friday and involve about 240 aircraft in about 1,600 sorties to “hone their wartime capabilities,” the U.S. 7th Air Force said in a statement. The drills have added to a series of joint exercises on land, sea and air in recent weeks, some of which have also included Japan, that have led to complaints and provocations from Pyongyang.

“If the U.S. does not want any serious developments not suited to its security interests, it should stop the useless and ineffective war exercises at once,” said the statement from the Foreign Ministry, which was released by the official Korean Central News Agency. “If not, it will have to totally take the blame for all the consequences.”

White House National Security Council spokeswoman Adrienne Watson said the joint exercises are “part of an annual, routine training schedule” designed to strengthen defense ties between the U.S. and South Korea, adding that, “we have made clear that we have no hostile intent towards the DPRK.”

“We reject the notion that they serve as any sort of provocation,” Watson said in a statement.

Since the end of September, when the USS Ronald Reagan aircraft carrier group was in the region for joint exercises, North Korea has fired off one of its biggest barrages of missiles under Kim, including two, short-range ballistic missiles that were tested last Friday.

The U.S., Japan and South Korea have warned that Kim could soon raise the stakes even higher with a nuclear test, which would be its first in five years and seventh overall. Washington, Tokyo and Seoul have all promised a harsh and coordinated punishment if Pyongyang sets off an atomic device, which would also be a violation of United Nations Security Council resolutions.

The test might be used to advance Kim’s pursuit of miniaturized nuclear warheads that he could mount on missiles to strike the U.S. allies of South Korea and Japan that host the bulk of America’s troops in Asia.

The North Korean leader is finding space to ramp up provocations and conduct tit-for-tat military moves as the Biden administration focuses on Russia’s war in Ukraine. Russia and China, two long-time partners of North Korea, have veto power at the UN Security Council and have shown no intent to punish Kim with extra sanctions.

Kim has ignored the Biden administration’s calls for him to return to nuclear disarmament talks that have been stalled for about three years. State media recently said that he reaffirmed his opposition to negotiations with the U.S. after declaring in September that North Korea would “never give up nuclear arms or denuclearize first.”

Bloomberg’s Jordan Fabian contributed to this report.