While tensions typically spike around the dates of the exercises, the situation generally calms afterward.

U.S. and South Korean military officials plan to move ahead with large-scale exercises later this month that North Korea, now finalizing plans to launch a salvo of missiles toward Guam, claims are a rehearsal for war.

The exercises are an annual event, but come as Pyongyang says it is readying a plan to fire off four “Hwasong-12” missiles toward the U.S. island territory and major military hub. The plan would be sent to leader Kim Jong Un for approval just before or as the U.S-South Korea exercises begin.

Called Ulchi-Freedom Guardian, the exercises are expected to run from August 21-31 and involve tens of thousands of American and South Korean troops on the ground and in the sea and air. Washington and Seoul say the exercises are defensive in nature and crucial to maintaining a deterrent against North Korean aggression.

The exercises were scheduled well before tensions began to rise over President Donald Trump’s increasingly fiery rhetoric and North Korea’s announcement of the missile plan, which would be its most provocative launch yet. Along with a bigger set of maneuvers held every spring, the exercises are routinely met by strong condemnation and threats of countermeasures from North Korea.

While tensions typically spike around the dates of the exercises, the situation generally calms afterward.

But the heightened military activity on the peninsula this time is a concern because it could increase the possibility of a mishap or an overreaction of some sort by either side that could spin into a more serious escalation. North Korea has been increasingly sensitive to the exercises lately because they reportedly include training for “decapitation strikes” to kill Kim Jong Un and his top lieutenants.

Pyongyang is also switching its propaganda machine into high gear by bringing in a large number of foreign journalists to ensure it gets global attention for an event next week in honor of its ruling Kim family on Mount Paektu, a dormant volcano that straddles the Chinese border and is something of a spiritual home for the regime.

Officials in Seoul confirmed Friday that the exercises are expected to begin without any delays, but refused to provide further details. According to the U.S. Department of Defense, Ulchi-Freedom Guardian involves about 40,000 troops, along with civilian South Korean government personnel who train their civil defense responses.

The possibility of escalation is made even more acute by the lack of any means of official communication across the Demilitarized Zone, though there has been no easing of the barrage of inflammatory comments in the U.S. and the North since new sanctions against North Korea were announced last week.

Keeping up his tough talk from his New Jersey golf resort where he is on a working vacation, Trump warned Kim Jong Un’s government to “get their act together” or face extraordinary trouble, and suggested his earlier threat to unleash “fire and fury” on North Korea was too mild.

Mr. Trump declined to say whether the U.S. is considering a pre-emptive military strike as he spoke to reporters before a briefing with his top national security advisers.

The president insisted the North had been “getting away with a tragedy that can’t be allowed.”

“North Korea better get their act together, or they are going to be in trouble like few nations have ever been in trouble,” Trump said, flanked by Vice President Mike Pence. Accusing his predecessors of insufficient action, Trump said it was time somebody stood up to Kim Jong Un.

Though tensions have been building for months amid new missile tests by the North, including the launch of its first intercontinental ballistic missile, the pace has intensified since the U.N. Security Council on Saturday passed sweeping new sanctions Trump had requested.

According to its reported plan, North Korea would fire four Hwasong-12 intermediate-range missiles over Japan and into waters around Guam, home to about 7,000 troops and 160,000 people.

North Korea said its military would finalise the plan “by mid-August,” then wait for Kim’s order. U.S. allies Japan and South Korea quickly vowed a strong reaction if the North were to follow through.

Mr. Trump echoed that threat Thursday, insisting if North Korea took any steps to attack Guam, its leaders would have reason to be nervous.

“Things will happen to them like they never thought possible, OK?” Trump said. He did not specify what they might be.