The prospect of a possible breakthrough summit between Washington and Pyongyang has left Tokyo jittery that U.S. President Donald Trump, under his banner of “America First,” may settle for a major policy compromise that prioritizes U.S. homeland security while disregarding allied Japan’s vulnerability to North Korean missiles, experts said Wednesday.

In his meeting with a high-level South Korea delegation Monday, North Korean leader Kim Jong Un was quoted by the South Korean government as saying he was open to talks with the U.S. to discuss denuclearization and the normalization of bilateral ties.

Despite the shifting ground, Prime Minister Shinzo Abe told Katsuyuki Kawai, his special diplomatic adviser currently in Washington, that Japan will continue to pressure the North for the time being, Kyodo News reported Wednesday. Kawai was quoted as telling reporters that Abe considers the latest overtures by the regime a sign that international sanctions and the increased monitoring of “ship-to-ship transfer” of goods involving North Korean vessels have been working.

Under Abe, who has persistently pursued a hard-line policy of heaping pressure on the regime, Japan maintains the position that no dialogue with the North is acceptable unless it takes concrete steps toward the “complete, verifiable and irreversible” dismantlement of its nuclear program.

Chief Cabinet Secretary Yoshihide Suga on Wednesday insisted Japan and the U.S. remained in lockstep with each other in this respect. “Since the latest announcement by Seoul, we have approached Washington on multiple levels to coordinate opinions.”

Citing a terse statement released by U.S. Vice President Mike Pence that emphasized Washington’s continued commitment to “maximum pressure” and its intention to see that the regime takes “credible, verifiable, and concrete steps toward denuclearization,” Suga said it was “obvious that Japan and the U.S. are on the same page.”

But any potential summit involving Kim and Trump could be a source of discomfort for Japan. Tokyo, experts say, is likely fretting over a scenario where Washington prioritizes having Pyongyang give up its development of nuclear-tipped intercontinental ballistic missiles (ICBM) capable of hitting the U.S. mainland, while overlooking the danger posed by shorter-range missiles to its key Asia allies, mainly Tokyo.

“One of the biggest fears of Tokyo is that the U.S. administration will embark on the talks with Kim under the spirit of ‘America First’ and accept a major compromise that only removes its own fears, i.e. ICBM development,” said Atsuhito Isozaki, an associate professor and a North Korea expert at Keio University.

Such an unwelcome scenario has been eerily signaled by the fact that it was only after 2016 — when Pyongyang made the necessary leap toward mastering the ICBM technology that posed a credible nuclear threat to the U.S. — that Washington actually “buckled down” to deal with the North, Isozaki said.

Kan Kimura, a political science professor and Korean affairs expert at Kobe University, agreed. Kimura said that the worst-case scenario for Tokyo would be a possible “Japan passing” by the U.S. and South Korea, where the two allies go ahead and negotiate with North Korea on terms that fail to fulfill Japan’s stated goal of completely ridding the isolated regime of its nukes.

Kimura said North Korea showed a willingness for denuclearization in an attempt to seize on an opportunity to negotiate with the U.S. It may be possible that the U.S. will lift sanctions on North Korea if Pyongyang agreed to suspend, instead of completely scrap, its nuclear and missile development, Kimura said.

But “even if their nuclear development was suspended, (the North) would still have Rodong missiles that may be loaded with nuclear (warheads). The missiles would not reach California or Hawaii, but they have the capability to strike Japan,” he said, adding that “the U.S. will no longer be fearful of the possibility of missiles hitting its shores if the North suspended its ICBM development.”

Kimura also said it is possible that prior to Kim’s meeting with the South Korean delegation, Washington and Seoul had secretly discussed its details while purposely keeping Japan out of the loop.

“The U.S.-Japan alliance may not be as strong as the Japanese believed it was,” he said, adding that Tokyo’s weaker presence as a player in dealing with Pyongyang under such a scenario would, in turn, make it even more difficult for it to secure the release of abductees kidnapped by North Korean agents in the 1970s and 1980s — one of the top policy priorities for the Abe administration.

Meanwhile, in the unlikely event that the U.S. — at the expense of Japan — makes a complete U-turn in its policy and inches toward rapprochement with the North, Tokyo, which has been largely dependent on the Washington in dealing with Pyongyang, would theoretically have little room for going its own way and proceeding with its current pressure-first tactics, Isozaki said.

But at the same time, the Abe administration’s hard-core “get-tough” attitude to date suggests that any pursuit of its own thaw with the North is not in the offing at the moment, he said.

“For now, the Japanese government will probably go all-out in trying to steer Washington away from the direction of dialogue, saying it’s meaningless,” Isozaki said.