The Republic of Korea has reportedly suspended the rollout of a controversial US missile defense system on its soil after its President Moon Jae-in ordered an environmental impact assessment.

This is expected to allow more time and room for Seoul to fully weigh the pros and cons of deploying the Terminal High-Altitude Area Defense and it is to be hoped it arrives at a more rational decision that accommodates the concerns of all parties involved.

The installment of the THAAD system in the ROK, a decision made during the administration of impeached and ousted president Park Geun-hye, has complicated the already combustible situation on the Korean Peninsula and worsened the ROK's ties with China.

The issue of THAAD has continued to cast a shadow over Sino-ROK relations despite some signs of improvement since Moon entered office last month.

On the campaign trail, Moon supported a THAAD review and vowed to consult China on the issue, which raised hopes THAAD's rollout would be suspended or even reversed.

Last week, Moon consolidated such hopes by ordering an investigation into the clandestine shipment of four more anti-missile launchers for the THAAD battery already installed in the country.

However, the optimism that engendered was dashed when Moon told visiting US Senator Dick Durbin on May 31 that the investigation is not about "trying to change the existing decision or sending a message to the United States".

Moon seems to be caught in a difficult situation: By reversing the decision to deploy THAAD, he will displease the United States; by giving the green light to it, he will definitely deal a fatal blow to the ROK's relations with China.

In fact, he can take his lead from the words of US Defense Secretary Jim Mattis, who, speaking during the Shangri-La Forum in Singapore over the weekend, quoted President Xi Jinping, saying "only if all sides live up to their responsibilities and come together from different directions can the nuclear issue on the peninsula be resolved as quickly as possible."

Mattis said those words "must be followed by actions by all of us".

No doubt, the controversies surrounding THAAD have all stemmed from the nuclear issue on the peninsula. But even though Moon has expressed his willingness to engage with the ROK's neighbor in the north, Seoul cannot defuse the crisis singlehandedly.

The US has stepped up collaboration with China over the issue, which has contributed to easing tensions on the peninsula.

This good momentum should be nurtured because communication and negotiation are the only feasible means for stakeholders to build consensuses and find solutions acceptable to all.