South Korea's new ambassador to the United States said Thursday that he will encourage Washington to play a "constructive role" in resolving tensions between Seoul and Tokyo that led to the South's decision to end a military information-sharing pact with Japan.

Lee Soo-hyuck, who was formally appointed this week, made the remark as concerns have grown over trilateral cooperation between the US and its two Asian allies after Seoul decided in August to withdraw from the General Security of Military Information Agreement (GSOMIA).

"Since the US has said it will play a constructive role, I will continue to call for its constructive role. I see that as an important task for me in the short term," he told reporters.

Washington has publicly expressed disappointment over Seoul's decision to pull out of the pact, seen as a rare platform for trilateral security cooperation. Yet it has also indicated willingness to help the two sides find ways to resolve their differences.

"I intend to find out what exactly the US meant when it said mediation would be difficult but they will play a positive role. I believe they are working on it, given that the time is coming," Lee said. GSOMIA is set to expire on Nov. 22.

Seoul's decision on GSOMIA came after Tokyo tightened its exports of certain chemicals vital to South Korea's mainstay tech industries, in apparent retaliation for last year's South Korean court rulings in favor of Korean victims of forced labor under Japan's 1910-45 colonial rule.

While Seoul and Tokyo have since seen their bilateral relations dip to the lowest point in years, hopes are rising for a breakthrough as South Korean Prime Minister Lee Nak-yon is set to attend Japanese Emperor Naruhito's enthronement ceremony in Tokyo next week.

Lee stressed that Seoul-Washington ties remain strong, downplaying concerns over a possible rift in the alliance stemming from regional security issues.

"I am well aware of the concerns but many US officials I have met recently told me that they do not think that way," he said.

"International relations are all about frictions and clash of national interests. It's natural that those things happen and diplomacy is there to resolve such problems."

On the US-China relations, he pointed out that studying their relationship is essential to the future of South Korean diplomacy, saying that he plans to create a research division at the embassy tasked with analyzing the topic in depth.

"I believe the future, history and policy of South Korea will hinge on the U.S.-China relations. We will set the wrong coordinates if we don't precisely analyze them."

Lee, a retired career diplomat and previously a ruling party lawmaker, was South Korea's first chief nuclear negotiator for the six-party talks involving the two Koreas, the US, China, Japan and Russia, when it was launched in 2003 with the goal of resolving the North Korean nuclear issue.

He also served as ambassador to Yugoslavia in 2002 and Germany in 2005, before entering politics in 2016.

Lee is set to leave for Washington next Thursday. (Yonhap)