South Korean President Lee Myung-Bak speaks during the 10th anniversary commemorative ceremony of the second naval battle of Yeonpyeong at the Navy's 2nd Fleet Command in Pyeongtaek, about 45 miles south of Seoul, on June 29, 2012. The speech came in lieu of a botched intelligence-sharing pack between Seoul and Tokyo. (Stringer-Korea/Reuters)

Japan and South Korea had planned on Friday to sign a new intelligence-sharing agreement that would show off their growing trust. But when Seoul unexpectedly backed out of the deal, the neighbors were left only with a new disagreement and a reminder of their long-running animosities.

The pact had been designed to allow Tokyo and Seoul to exchange classified information on their mutual concerns — specifically, China’s military and North Korea’s weapons program.

But one hour before the scheduled signing, South Korean officials notified Japan’s Foreign Ministry that they were postponing, a Japanese government spokesman said. The planned agreement had stoked fury in Seoul, with media and ruling-party politicians ripping the government for joining hands with the country that used to be South Korea’s brutal colonial ruler.

A Japanese Foreign Ministry spokesman, Masaru Sato, said Tokyo was “disappointed” by the about-face.

“Our sense is, the agreement should have been signed today,” Sato said.

The General Security of Military Information Agreement would have been the first military pact between the two countries since World War II.

It was supported by Washington, where officials looking for new ways to handle China’s military rise have long urged their two closest East Asian allies to cooperate more and to bury the resentments that trace back more than a century.

And for much of this week, it looked like the pact would happen. South Korea’s cabinet approved the military agreement on Tuesday. Japan on Friday prepared to hold the ceremony in a room at its Foreign Ministry.

But South Korean President Lee Myung-bak faced intensifying pressure to delay the signing — from both the left and the right. The conservative ruling party chief policymaker on Friday said it was “inappropriate” to go ahead with a plan that countered public sentiment. A major liberal newspaper, the Hankyoreh, criticized the central government for pushing ahead with the pact before discussing it in the National Assembly.

South Korea already has agreements or pending agreements to share military secrets with 24 other countries, the Hankyoreh editorial noted. “But a military agreement with Japan is a different matter,” the editorial said. “Public opinion here simply will not tolerate us joining forces militarily with a country that refuses to budge on historical matters.”

Japanese government officials on Friday emphasized that the signing had been deferred, not cancelled. A South Korean Foreign Ministry spokesman, Cho Byung-jae, said Seoul is still discussing the next steps, according to South Korea’s Yonhap news agency.

South Korean resentment of the Japanese military traces back to World War II, when soldiers forced Korean women to become front-line sexual slaves.

Although the countries have become strong trading and cultural partners, they have also squabbled in recent years over their dueling claims to a group of desolate, rocky islets — home to two permanent residents. One South Korean ministry building shows a live feed of the rocks on a massive flat-screen television in its lobby.