TOKYO -- Deterring aggression by reaffirming pledges to counter North Korean nuclear strikes with the same force needs to take place in tandem with reassuring the regime of its safety, a Japanese expert said of curbing North Korea’s provocations.

The strategy of using the US nuclear umbrella is what Seoul and Washington have been doubling down on since April when the two allies agreed to bolster deterrence on the North’s weapons tests. President Yoon Suk Yeol, who came to power in May last year, considers the April agreement the backbone of his North Korea policy.

“President Yoon Suk Yeol has done pretty well diplomatically (on the North Korea issue),” Tadashi Kimiya, a Tokyo University professor specializing in Korean studies, said in an interview with reporters in Tokyo.

“But South Korea needs its own separate policy on the North,” Kimiya noted, suggesting the South focus just as much on making the North feel safe. Seoul could do that alone or together with Washington so the North feels less threatened and potentially dial back provocations, according to Kimiya.

Japan, part of a three-way partnership with the South and the US to coordinate security responses to threats from North Korea, could contribute to efforts by starting negotiations to establish diplomatic relations with the North, Kimiya added.

For now, Pyongyang could rather accuse the Yoon administration of “double standards,” Kimiya said, referring to Seoul’s decision to suspend part of a 2018 military pact on reducing cross-border hostilities. The South said the Nov. 21 rocket launch by the North that put a spy satellite into orbit warranted the shift.

“Was that really necessary?” Kimiya said. “If the North Koreans conducted a nuclear test, then that’s understandable. But the South Koreans also plan to do the same,” Kimiya added. His comments were made before South Korea’s Dec. 2 launch of the country’s first locally made spy satellite into orbit.

Unlike Pyongyang, Seoul does not face United Nations sanctions banning launches including space rocket firings that use ballistic missile technology. The launch from Vandenberg Space Force Base in California was successful, Seoul’s Defense Ministry said of the satellite atop a SpaceX Falcon 9 rocket. The military plans to have four more up in space by 2025.

Kimiya said he expects to see reinforcing deterrence take center stage as Seoul, Washington and Tokyo coordinate policy on the North, as long as the isolated country defying UN sanctions does not reverse the course.

National security adviser Cho Tae-yong and his US and Japanese counterparts -- Jake Sullivan and Takeo Akiba, respectively -- pledged last week a new joint initiative to deal with Pyongyang’s military threats and cyber activities funding its weapons programs. Details about the way the plan could pan out were not disclosed.

Whether the tighter three-way ties could be undone, in part or entirely, as America elects a new president next year remains to be seen, according to Kimiya.

“If former US President Donald Trump returns to the White House for a second term, there is some unpredictability in the way policy gets drawn up,” Kimiya said of the US leader known for transactional diplomacy that affords longstanding relationships less credit than they have usually deserved.

“But I don’t see a drastic pivot, so the guiding framework governing trilateral cooperation looks like staying, broadly speaking that is,” Kimiya said.

This article was written in partnership with the Joint Press Corps.