The former deputy defense secretary for both Barack Obama and Donald Trump is criticizing the substance and framing of Trump’s abrupt cancellation of joint military exercises with South Korea as a “pretty substantial concession” to North Korea—something that both Russia and China could turn to their advantage elsewhere.

“This seems like a pretty substantial concession on our part,” Robert O. Work, the number-two official at the Pentagon from April 2014 to July 2017, told The Daily Beast.

“Given that there were no really concrete concessions on the side of the North Koreans, I’m saying, wow, this was a pretty big concession to make without any conditions or any expectations of some type of concomitant North Korean concession.”

Work said he was “of two minds” about pausing the U.S.-South Korea drills, since Trump and Defense Secretary James Mattis can resume them should Pyongyang demonstrate intransigence on ending its nuclear weapons and long-range missile programs.

“On the other hand, if you’re going to try to convince North Korea that the administration’s approach is quite different from the past,” Work said, “this is one of the things that is pretty reversible. If North Korea begins to stall or not make any forward momentum, this is something you could turn back on rather quickly.”

Work who is widely respected by defense wonks in both parties, was the seniormost Obama administration official to carry over into the Trump administration, assisting Mattis, his fellow former Marine officer, for about six months.

“ If I was a Chinese or a Russian strategist, any time that I could get the United States to stop exercising near my national territory, I would think that would be a good thing. ” — Robert O. Work

Although Work was out of the administration at the time, he said that “it was about six months ago that Russia and China floated this idea” for halting the U.S.-South Korean drills as a gesture to Pyongyang. “The administration, with the Pentagon’s backing, elected not to do so.”

Work warned that Trump’s language could be a lever for Russia and China to press the U.S. on similar military exercises with allies far from the Korean Peninsula.

“The Russians could easily say that exercises in Europe with NATO are provocative, and they are also expensive. So I think the president has opened a door that he didn’t need. All he had to do, in my view, if he was intent on using this as a bargaining chip or a negotiating chip, he could have just announced it and not said anything more. The fact that he said that they were provocative and expensive opens the door for many, many other exercises to be questioned,” Work said.

“If I was a Chinese or a Russian strategist, any time that I could get the United States to stop exercising near my national territory, I would think that would be a good thing,” the former deputy defense secretary continued.

Work wasn’t the only one who was surprised or confused by Trump’s announcement that he was cancelling those drills, apparently. Shortly after Trump spoke after meeting in Singapore with Kim Jong-un, The New York Times quoted a spokesperson for the U.S. military command in South Korea who seemed to be blindsided by the exercise cancellation. A Pentagon’s statement yesterday “welcom[ing] the positive news coming out of the summit,” from chief spokesperson Dana White, sidestepped the joint exercises. As well, there was some confusion among congressional Republicans speaking with Vice President Mike Pence on Tuesday as to how extensive the announced exercise pause will be.

Work added, “My understanding is this caught our allies South Korea and Japan both by surprise. And my understanding is it also caught the Department of Defense by surprise.” If so, he expected Secretary of State Mike Pompeo, who is currently in Seoul, to make reassuring both allies a “front and center” priority.

“Under normal circumstances, this is something that would have been discussed intensively within the administration, and also discussed intensively with our allies before it was announced,” Work said. “On the merits, I believe that [pausing the exercises] has the potential to cause problems within the alliance.” But given the reversibility of the drilling pause, “this is more about how it plays out amongst our allies.”

Pompeo told reporters in Seoul on Thursday that Trump told Kim “that the condition precedent for the exercises not to proceed was a productive, good-faith negotiations being ongoing. And at the point it’s concluded that they are not, the president’s commitment to not have those joint exercises take place will no longer be in effect.”

A former top Asia policy official in the Obama Pentagon, Abraham Denmark, sounded similar notes about cancelling the joint exercises.

“Postponing or freezing exercises in itself is not a problem,” said Denmark, a former deputy assistant secretary of defense. “The real challenge is that they were given up unilaterally, without North Korea giving anything up in return.”

The Pentagon did not have immediate comment on whether Trump provided the department with advance notice of the pause.

In announcing the pause, Trump called what he termed exercises “very expensive” and “very provocative,” something that struck Work as an adoption of Pyongyang’s language.

Asked about Trump’s language choice, Pompeo said the president’s “intention here was to put us in a place where we get the opportunity to have productive conversations connected to the denuclearization of North Korea.”

“The use of these words was, I thought, unfortunate,” Work said, “because it mirrors the wording that North Korea has used for quite some time.”