US Defense Secretary Mark Esper and his Japanese counterpart Taro Kono met in Guam on Saturday to discuss key regional security issues, including threats from North Korea. They agreed on the importance of ensuring that UN sanctions on the North are fully implemented for the abolition of the recalcitrant regime’s nuclear arsenal and ballistic missiles.

Esper and Kono raised objections to China’s actions that destabilize the region, pledging to strengthen cooperation in building the posture to prevent any attempt to change the status quo by force. They also discussed ways to build an integrated missile defense system, including the co-development of a new type of interceptor missiles, and improve military intelligence-sharing arrangements.

It was unnatural for the US and Japanese defense chiefs not to be joined by their South Korean counterpart in discussions on such sensitive security matters, to which Seoul should pay due heed. Actually, it was South Korea that shunned what was supposed to be a trilateral meeting among the top defense officials of the US and its two key Asian allies.

Earlier this year, the US proposed three-way talks in Guam, but Seoul’s Defense Ministry dragged its feet in responding to the proposal.

“We’ve had close consultations with the US and the Japanese sides since May for trilateral defense ministers’ talks under the notion that South Korea-US-Japan security cooperation is crucial,” the ministry said in an Aug. 21 statement, adding the schedule has yet to be fixed due to COVID-19 and different schedules of the three defense chiefs.

At the time, a local news agency quoted a “Seoul source” -- believed to be a ministry official who wanted anonymity -- as saying it does not seem to be a plausible option for South Korean Defense Minister Jeong Kyeong-doo to make an overseas trip given the worsening domestic coronavirus situation. It made little sense to cite concerns over the coronavirus pandemic as a reason for Jeong’s failure to travel to Guam for the envisioned trilateral meeting.

The coronavirus situation has been more serious in the US and Japan than here. Furthermore, the defense minister is not tasked with containing the spread of COVID-19. For South Korea’s defense chief, there can hardly be a more important schedule than a meeting with US and Japanese counterparts on key security issues.

Contrary to their mention of COVID-19 in indicating the improbability of Jeong’s trip to Guam, Seoul officials stressed that a top Chinese official’s recent visit to Busan had nothing to do with the pandemic.

Yang Jiechi, a member of the Chinese Communist Party’s Politburo, chose the southern port city instead of Seoul for his second visit here in two years, sparking speculation that the move, which went against diplomatic courtesy, had been prompted by concerns over the resurgence in coronavirus cases in the capital.

After a meeting between Yang and Suh Hoon, national security adviser to President Moon Jae-in, Cheong Wa Da said the two sides agreed to finalize Chinese President Xi Jinping’s “early visit” to South Korea once the coronavirus situation here stabilizes.

Moon and his aides hope Xi’s visit here would give a significant boost to their push for reconciliation with North Korea. They are pressing ahead with cross-border projects with the North, many of which might run the risk of violating international sanctions imposed on the totalitarian state for its nuclear and ballistic missile tests.

The Moon administration was apparently reluctant to attend the defense ministers’ meeting with the US and Japan, as it was expected to affirm the firm implementation of sanctions against Pyongyang and criticize China’s increasingly coercive behavior.

The North continues to improve its nuclear and missile capabilities, urging its people to be dedicated to building a self-reliant economy.

China seems to be dangling the possibility of Xi’s trip to draw South Korea into its fold or push it to remain at least neutral in its intensifying rivalry with the US. During his meeting with the South Korean presidential security adviser, Yang explained China’s position on the escalating Beijing-Washington rift, giving a veiled warning that Seoul should not go against Beijing’s stance.

A day before the meeting between US and Japanese defense chiefs, two Russian military planes intruded into South Korea’s air defense identification zone for the second time in 10 days. Russian military aircraft violated the country’s air space last year after a joint air drill with China over the East Sea.

To cope with this destabilizing security environment, South Korea needs to strengthen its alliance with the US and by extension the trilateral cooperation with Japan.