Seoul has rejected a proposal to meet on the sidelines of an international security forum starting Tuesday in Singapore to discuss the diplomatic row that has erupted over Tokyo's claim to South Korea-held islets in the Sea of Japan, Japanese officials said Thursday.

"It's regrettable but I received a report (from subordinates) that it is difficult to arrange a Japan-South Korea foreign ministerial meeting in Singapore," Chief Cabinet Secretary Nobutaka Machimura said Thursday afternoon in Tokyo.

"I believe it is very important for diplomats in charge to meet and have frank discussions in such a (difficult) situation."

Foreign Ministry sources had said Tokyo was willing to arrange ministerial talks in Singapore to demonstrate the overall soundness of the relationship despite the most recent flap over the long-standing territorial dispute over Takeshima, known as Dokdo in South Korea.

The failure to arrange a meeting is the first setback for Japanese diplomacy following Tokyo's decision to post new teaching guidelines for junior high schools that permit publishers to lay out Japan's claim to the islets in textbooks.

South Korean Ambassador Kwon Chul Hyun, who was recalled to Seoul, has warned that the new guidelines could jeopardize Seoul's diplomatic partnership with Tokyo.

"The worst thing happened at a time when South Korea and Japan need to cooperate as partners in various aspects internationally," South Korea's Yonhap new agency quoted Kwon as saying at a press briefing.

"The most important thing is the six-way talks (on denuclearizing North Korea)."