South Korea's foreign ministry said Thursday it will press ahead with a controversial decision to sign its first military accord with Japan since its colonial occupation of the Korean peninsula.

Local reports said a day ago South Korea's Cabinet endorsed the pact, called the General Security of Military Information Agreement (GSOMIA), which allows the two sides to exchange military intelligence on the Democratic People's Republic of Korea (DPRK) and its nuclear and missile programs.

The clandestine Cabinet approval, which effectively concluded domestic procedures to seal the deal, immediately copped criticism from opposition lawmakers and civic activists who warn the accord will provoke anti-Japan sentiment and generate regional tension.

Such concerns pressured the South Korean government last month into suspending the signing of a separate military agreement with Japan, called the Acquisition and Cross-Servicing Agreement (ACSA).

The deal, if signed, would have allowed exchanges of supplies including fuel and weapons between the South Korean military and Japan's Self-Defense Forces.

"We are well aware that domestic procedures for the accord didn 't go entirely smoothly and we humbly accept such criticism," foreign ministry spokesman Cho Byung-je said during a press briefing.

Still, the government believes the accord will be signed as early as Friday after Japan's Cabinet approval, Cho added.

Shin Kak-soo, Seoul's top envoy to Tokyo, and Japanese foreign minister Koichiro Gemba are expected to sign the watershed pact in Tokyo.

Liberal and progressive lawmakers have voiced strong opposition to the agreement, which they say will embolden Japanese right-wing extremists and stir up fresh military tension in Northeast Asia.

"The accord, which was rushed through the Cabinet, is invalid," the main opposition Democratic United Party said during a briefing. "We'd like to make it clear that the decision should be reached only after parliamentary discussions."

The left-leaning Unified Progressive Party, along with an association of liberal civic groups, issued a statement suggesting the United States was behind the hush-hush deal.

The United States, which has troops stationed in both South Korea and Japan, has placed an increasing emphasis on trilateral security cooperation in part by initiating joint drills and talks involving top defense officials.

"The purpose of the accord is to facilitate the move by the US to build a missile defense system (in the region)," civic activists said in a statement read out during a rally in central Seoul earlier in the day.

The foreign ministry here has rejected allegations of Washington's influence, saying there are "misunderstandings" and " excessive conjecture" surrounding the agreement.

"The pact is sort of like a vessel -- what you choose to store in it is an entirely different issue," the spokesman said.