South Korea's new President Lee Jae Myung and Japanese Prime Minister Shigeru Ishiba vowed to deepen a relationship prized by Washington and closely watched by China and North Korea, as the pair met for their first summit.
The two leaders spoke on the sidelines of the G7 meeting in Canada on Tuesday.
"Under the current strategic environment, the importance of Japan-South Korea relations and Japan-U.S.-South Korea cooperation has not changed at all - rather, it has become more important," Ishiba said later at a press conference.
Lee said the two countries have an "inseparable" relationship like "neighbours who share a front yard."
The leaders discussed maintaining and strengthening trilateral cooperation with the United States to respond to geopolitical crises including the North Korea issue, his office said in a statement.
Ties between the U.S. allies have often been strained, rooted in historical disputes stemming from Japan's colonial rule over the Korean peninsula from 1910-1945.
The United States has pressed the two countries to cooperate more closely to confront regional challenges such as North Korea's nuclear threat and rising competition from China.
Lee told Ishiba that cooperation would be mutually beneficial amid difficulties in the international trade environment and called for the improvement of ties in a "future-oriented manner".
In recent years, Lee had been harshly critical of efforts by his predecessor, conservative Yoon Suk Yeol, to mend ties with Tokyo, and his stance as president will be closely watched by the United States and China.
He once called Yoon a "puppet" of Japan and decried a landmark 2023 summit with former Japanese Prime Minister Fumio Kishida as the "most humiliating moment" in South Korea's diplomatic history.
Lee, who moderated his rhetoric before assuming office this month, has said pragmatism is key to his diplomacy and he would continue with security cooperation between South Korea, Japan and the U.S.
"In terms of early diplomatic scorecard, President Lee isn't only saying the right things, he's doing things in the right order," said Leif-Eric Easley, a professor at Ewha University in Seoul.
"His first travel abroad for the G7 summit demonstrates South Korea's global governance contributions with fellow middle powers like Canada that are committed to defending the international order," Easley said.
Lee's visit to Canada for the G7 summit marks his first international trip as president, since winning the June 3 snap presidential election called after Yoon was impeached and removed for briefly imposing martial law last year.
During the summit, Lee also met with other world leaders, including British Prime Minister Keir Starmer, where he called for progress on updating the free trade agreement between the two countries, according to Lee's office.
In a meeting with Indian Prime Minister Narendra Modi, Lee promised to deepen strategic cooperation and highlighted South Korean investments in the South Asian country.
