Last week's remarks by Mr Abe angered China and South Korea

The study follows calls by some 130 MPs from Mr Abe's Liberal Democratic Party for the issue to be reviewed.

Tokyo apologised in 1993 for its role in setting up army brothels, but the MPs believe the apology went too far.

Mr Abe last week publicly questioned whether "comfort women" - mainly Chinese and Korean - were coerced.

His remarks angered neighbouring China and South Korea.

Many historians say Japan compelled up to 200,000 women to become sex slaves during the war.

But some Japanese scholars deny that force was used to round up the women, blaming private contractors for any abuses.

US Congress debate

"The party [the LDP] will conduct the research," Mr Abe told reporters in Tokyo.

"The government will co-operate as needed by providing materials," he said.

Earlier, the prime minister rejected a call from about 130 LDP lawmakers for the government itself to commission the inquiry into the controversial issue.

The MPs are demanding that Tokyo water down its statement of apology to the comfort women.

Mr Abe last week angered Beijing and Seoul with remarks that appeared to question Japan's role in forcing the women to work in the army brothels.

However, Mr Abe said he stood by the 1993 apology, which acknowledged that the military set up and ran brothels for its troops during the war.

Chinese Foreign Minister Li Zhaoxing said Japan should face up to history and take responsibility for its army's use of sex slaves.

South Korean Foreign Minister Song Min-soon described Mr Abe's remarks as "not helpful".

The US House of Representatives is currently considering a non-binding resolution calling on Tokyo to "formally acknowledge, apologise and accept historical responsibility" for the treatment of the women.

Many former comfort women are still seeking compensation from the Japanese government for their experiences.