US Deputy Secretary of State Wendy Sherman answers questions in a press conference at the State Department in Washington, DC.

A joint press conference in Washington by the deputy foreign ministers of Japan, South Korea, and the US has been canceled over a territorial dispute, with US Deputy Secretary of State Wendy Sherman being left to answer questions on her own.

South Korea’s First Vice-Foreign Minister Choi Jong-kun and Japan’s Vice-Foreign Minister Takeo Mori had been due to appear alongside Sherman on Wednesday after the three countries discussed regional tensions, but Sherman stood alone at the podium to answer questions.

Sherman did not specify what stopped the joint press conference from happening but said, There are some bilateral differences between Japan and the Republic of Korea that are continuing to be resolved. And one of those differences, which is unrelated to today’s meeting, has led to the change in format for today’s press availability.

She told reporters that the three-hour meeting with her Japanese and South Korean counterparts had been constructive (and) substantive.

The three officials discussed freedom of navigation and overflight in the South China Sea and the three countries’ commitment to advancing democratic values and human rights, and restated their commitment to maintaining an inclusive, free, peaceful, stable, and open Indo-Pacific region, Sherman said.

She said the US, Japan, and South Korea opposed activities that undermine, destabilize or threaten the rules-based international order in the Indo-Pacific region and in the Taiwan Strait.

Hours later, Masashi Mizobuchi, a spokesperson at the Japanese Embassy in Washington, said Japan had lodged a strong protest over a visit to the disputed islands by the head of South Korea’s national police agency, a sub-cabinet-level post.

The islets are indisputably an inherent part of the territory of Japan and under these circumstances, we have decided that it is inappropriate to hold a joint press conference, the spokesman said.

There was no immediate comment from South Korea.

Kim Chang-yong, the commissioner-general of South Korea’s national police agency, arrived in the disputed islands known as Takeshima in Japan and Dokdo in South Korea on Tuesday, media reports said, in the first visit by the country’s police chief in 12 years. The islands are controlled by Seoul but claimed by Tokyo.

Although Japan and South Korea are considered key US allies in the Asia Pacific region, they have serious disagreements over a series of issues besides the islets, including trade and compensation for victims who were forced to work in Japanese firms and military brothels during Japan’s 1910-45 colonial rule.