SEOUL, South Korea — President Park Geun-hye on Tuesday approved a military intelligence-sharing pact with Japan aimed at countering the North Korean threat, a move that angered South Korean opposition parties, which want to impeach Ms. Park over a corruption scandal.

The United States, an ally of both South Korea and Japan, has pressed them to increase military cooperation so the three countries can more effectively monitor and confront threats from the North, whose development of nuclear arms and missiles has been accelerating. Currently, Japan and South Korea use Washington as an intermediary when sharing intelligence on North Korea.

But South Koreans are wary of cooperating too closely with Japan, which ruled Korea as a colony for 35 years until the end of World War II. Many of the protesters who have been demanding that Ms. Park resign over the corruption scandal have also insisted that she cancel the negotiations with Japan.

Ms. Park has been accused of conspiring with a friend, Choi Soon-sil, to extort millions from big businesses. Her polling numbers have reached record lows, and huge crowds have gathered in Seoul, the capital, and other major cities to demand that Ms. Park step down or face impeachment.

Prosecutors further undermined Ms. Park on Sunday by identifying her as a criminal accomplice while indicting Ms. Choi on extortion charges. As a sitting president, Ms. Park cannot be indicted.

Since the scandal engulfed her administration, Ms. Park has made moves to assert her leadership, such as making high-profile government appointments. Critics have charged that the talks with Japan were another attempt to establish her authority and rally her conservative supporters, who favor the deal. Her government has denied this, saying that the pact was needed to counter the threat from Pyongyang.

The main opposition Democratic Party said Tuesday that Ms. Park would be remembered as a “traitorous president” because of the deal with Japan.

“We cannot restrain our anger at President Park’s arrogance,” the party said in a statement. “She is not satisfied with parlaying the government through her unprecedented scandal; now she is trying to ruin diplomacy and national security too.”

Yoshihide Suga, the Japanese chief cabinet secretary, said Tuesday at a news conference in Tokyo that the government wanted to “work for an early signing” of the agreement but did not comment further, the Kyodo news agency reported.

Many South Koreans harbor strong resentment over Japan’s harsh colonial rule, and any moves by Japan to expand its military role in the region stir painful associations here.

In 2012, a similar intelligence-sharing deal with Japan was put on hold at the last minute after a domestic backlash in South Korea. The government’s sudden announcement that the talks would resume came a month ago, after the scandal involving Ms. Choi had erupted.

The pact, which was approved earlier Tuesday by Ms. Park’s cabinet, will take effect at a signing ceremony Wednesday morning, officials said.