The recent attendance by four Asia Pacific leaders at the NATO summit reflects a “consequential shift” in the US transatlantic security partnership which Washington seeks to expand to better counter China, a senior US diplomat told Reuters.

In an interview in Seoul, Derek Chollet, counselor of the US Department of State who serves as a senior policy advisor to Secretary Antony Blinken, said he sees “great potential” for cooperation between South Korea and NATO, built on previous exchanges including global efforts to help Ukraine and European countries joining RIMPAC military exercises in Asia.

“I think one of the most consequential shifts we’ve seen over the decade is the growing relationship between our transatlantic partners and our partners here in the Indo Pacific,” Chollet said.

Last month, Yoon Suk-yeol became the first South Korean president to attend a NATO summit in Spain, as he looks to play a bigger global role and forge European partnerships in the face of North Korea’s evolving nuclear threats.

The participation of Yoon and leaders of Japan, Australia and New Zealand, as well as NATO’s newly adopted strategy concept that cited China as a concern for the first time, was “truly historic” and “the beginning of what could be a very close partnership,” Chollet said.

“I vividly recall a decade ago trying to talk to European allies about the importance of the Indo Pacific and having a hard time getting them to be able to pay much attention. That has changed fundamentally,” he said.

“The foundation or the principle of our approach to China is ... aligning with partners and allies.”

Chollet also expressed hopes for stronger trilateral security cooperation among the United States, South Korea and Japan despite strained ties between Seoul and Tokyo due to wartime history feuds.

The death of former Japanese Prime Minister Shinzo Abe was a “terrible tragedy” and “horrific murder,” but his legacy and vision for the Indo Pacific could provide a chance to further energise trilateral efforts, he said.

“There’s a lot we can do together, whether it's military exercises, or cooperation on issues like global health,” Chollet said.

“We believe strongly that it's in our interest and Japan and Korea’s interests for the two countries to have strong ties,” he added, vowing to help both sides resolve differences if needed.