A longstanding territorial dispute between South Korea and Japan derailed a trilateral press conference in Washington, laying bare the strained relationship between the key US allies.

US Deputy Secretary of State Wendy Sherman faced the press alone following talks on Wednesday, after Japan protested a recent visit by South Korea's police chief to islets administered by Seoul but claimed by Tokyo.

"As has been the case for some time, there are some bilateral differences between Japan and the Republic of Korea that are continuing to be resolved," she said, without elaborating on the dispute that led to the absence of the Japanese and South Korean vice foreign ministers.

"And one of those differences which is unrelated to today's meeting, has led to the change in format for today's press availability."

Japan said it objected to the conference because South Korea's national police chief visited the disputed islets, which are called Dokdo by Seoul and Takeshima by Tokyo.

A Japanese embassy spokesman in Washington said the islets are "indisputably an inherent part of the territory of Japan" and that Tokyo had lodged a protest with Seoul over the visit.

"Under these circumstances, we have decided that it is inappropriate to hold a joint press conference," the spokesman said.

South Korean vice foreign minister Choi Jong-kun confirmed that his Japanese counterpart Takeo Mori did not attend the press conference over "the issue surrounding our police chief's visit to Dokdo."

US Deputy Secretary of State Wendy Sherman said 'bilateral differences' between Japan and South Korea derailed a jointed press conference in Washington after deputy foreign ministers from the three allied states met for talks
US Deputy Secretary of State Wendy Sherman said 'bilateral differences' between Japan and South Korea derailed a jointed press conference in Washington after deputy foreign ministers from the three allied states met for talks AFP / Pablo PORCIUNCULA

Sherman said the talks had been "very constructive," which "demonstrates exactly why the trilateral format with the United States, Japan and the Republic of Korea is so important and powerful."

Tokyo and Seoul have had strained relations for decades due to Japan's brutal colonial rule over the Korean peninsula between 1910 and 1945.

Flare-ups are a source of concern for Washington, which fears tensions between its two closest Asian allies could have repercussions for regional security.

During the trilateral meeting on Wednesday, the three sides reaffirmed their "shared commitment" to the "complete denuclearization of the Korean peninsula," said Sherman.

She renewed President Joe Biden's offer of dialogue with North Korea, which so far remains unanswered.

"The United States does not harbor hostile intent for the DPRK. We believe that diplomacy and dialogue are essential" to ridding the peninsula of nuclear weapons, said Sherman, referring to North Korea by its official title.

She added that Washington, Tokyo and Seoul oppose "activities that undermine, destabilize or threaten the rules-based international order" in the Indo-Pacific region and in the Taiwan Strait, a clear warning to China.