US President Donald Trump's unilateral pledge to end US military exercises with South Korea has emerged as a significant concession in his historic summit with North Korean leader Kim Jong Un.

It potentially halts a practice that US officials have long said is important to a decades-old military alliance.

The exercises are held several times each year, focusing on everything from warding off a North Korean attack on its neighbour to the south to "decapitation" strikes aimed at killing key members of the Kim regime.

North Korea has traditionally responded to them angrily, while the governments in Seoul and Washington have said they were defensive in nature and part of the "ironclad" US-South Korea alliance designed to ward off North Korean aggression.


Trump seemingly downplayed the significance of the exercises during a news conference following his summit in Singapore with the North Korean leader, in which Kim broadly agreed to end his nuclear weapons programme without providing specifics on how he would do so.

"We will stop the war games which will save us a tremendous amount of money," Trump said. "Unless and until we see the future negotiations is not going along like it should. We will be saving a tremendous amount of money. Plus, it is very provocative."

Trump added that the United States has "done exercises with South Korea for a long time," but that it would be "inappropriate" to continue while hammering out details to their deal.

"We call them war games. I call them war games," he said. "They are tremendously expensive. The amount of money we spend on that is incredible. South Korea contributes, but not 100 per cent which is a subject that we have to talk to them about also. That has to do with the military expense and also the trade. We actually have a new deal with South Korea. We have to talk to them. We have to talk to countries about treating us fairly. We pay for a big majority of them."

Trump added in an interview with ABC News that he had questioned what the exercises cost, noting that "we're flying planes in from Guam, we're bombing empty mountains for practice."

But he also left open the possibility that they could continue, saying that he wanted to stop them "unless for some reason we're unable to go further."

In a statement, the top US military headquarters in South Korea said that they have "received no official updated guidance on execution or cessation on any upcoming training exercises."

Randall Schriver, the Pentagon's assistant secretary of defence for Asian and Pacific security affairs, was in Singapore for the summit as part of the US delegation, and will return to Washington as the Pentagon considers its next moves.

A US F-22 Raptor stealth fighter jet lands as South Korea and the United States conduct the Max Thunder joint military exercise in May. Photo / AP file
A US F-22 Raptor stealth fighter jet lands as South Korea and the United States conduct the Max Thunder joint military exercise in May. Photo / AP file

Abraham Denmark, a deputy assistant secretary of defence for East Asia affairs during the Obama Administration, said that the US has previously cancelled military exercises with South Korea while attempting to negotiate with its neighbour to the north. But Trump calling them "provocative" could be an issue in the future, considering both North Korea and China have traditionally done so, he said.

"I think it's a characterisation that the US may come to regret if and when we decided to restart joint exercises with South Korea," Denmark said.

Trump disclosed no price tag on the exercises, and the Pentagon did not respond to requests for that information. With dozens of aircraft and some ships involved in some of them, they do collectively cost millions of dollars, but the operations are part of the Pentagon's plans to stay prepared for all possibilities, including war. They also could be replaced by other forms of training with similar costs.

The next major military exercise that had been scheduled between the US and South Korea was due to begin in August. Last year, that exercise, called Ulchi-Freedom Guardian, involved about 17,500 US troops and focused heavily on computer-simulated exercises.

The most significant exercises are held in the spring. One of them, Foal Eagle, involves field maneouvers, with about 11,500 US troops and 290,000 South Koreans participating. The second, Key Resolve, focuses more on command-and-control preparations, with a heavy reliance on computer simulation and about 12,200 US troops and 10,000 South Koreans involved, the Pentagon said in the spring.

The Pentagon has explicitly disputed in the past that the exercises are provocative, as Trump said yesterday.

"Our combined exercises are defence-oriented and there is no reason for North Korea to view them as a provocation," Marine Lieutenant-Colonel Christopher Logan, a Pentagon spokesman, said in a statement in March. "While we will not discuss specifics, the defensive nature of these combined exercises has been clear for many decades and has not changed."