TOKYO: Talks between Japan's centre-left Democratic Party and two prospective junior coalition partners went into the night Tuesday as they tried to form a government following last month's elections.

Senior party officials of the Democratic Party of Japan (DPJ) and the smaller groups were attempting to reach compromise on defence policy and issues that touch on the country's wartime history, media reports said.

The secretary-general of the DPJ, Katsuya Okada, was meeting the leaders of the Social Democratic Party (SDP) and the People's New Party (PNP) behind closed doors in the Diet parliament building.

The DPJ's incoming prime minister, Yukio Hatoyama, earlier voiced confidence that the talks would conclude by the end of the day.

"I think we'll reach an agreement," he told reporters in the morning, a day after he was forced to postpone an announcement of key cabinet appointments after ideological clashes with the prospective junior coalition partners.

Hatoyama is set to take over next Wednesday from Prime Minister Taro Aso after the DPJ defeated his conservative Liberal Democratic Party (LDP) in an August 30 election, ending its more than half-century of almost unbroken rule.

Aso, who is expected to step down as LDP president just before Hatoyama is elected in Wednesday's parliamentary session, apologised for his party's vote defeat, voicing "shame, regret and sorrow."

But he vowed that in opposition "I want the party to be reborn as a fighting party to regain power."

The DPJ -- which has never been in government -- needs the support of the two smaller parties in the upper house, the chamber which can block or stall legislation, despite its large incoming majority in the lower house.

Once a coalition is agreed, Hatoyama can announce some of his key cabinet appointments, who would be officially confirmed when he takes office.

Hatoyama earlier said he wanted Okada, 56, a former DPJ leader and one-time trade ministry technocrat, to become his foreign minister.

Veteran politician Hirohisa Fujii, 77, has been named in press reports as the front-runner for the post of finance minister.

The main sticking points in the coalition talks have been in foreign and security policy, reports said, with the Social Democrats stressing Japan's pacifist stance enshrined in the post-World War II constitution.

Media reports said the SDP wants Hatoyama's party to commit in writing to the promise of ending a naval refuelling mission in the Indian Ocean that has supported US-led operations in Afghanistan.

They have also long opposed the presence of a US military base on southern Okinawa island, where tensions have flared between residents and American service members in the past, and want it scaled down quickly.

The SDP has further demanded that the coalition formally commit itself to an apology for Japan's World War II militarism, reiterating a 1995 statement by former Socialist Party premier Tomiichi Murayama, the Yomiuri Shimbun reported.

The head of the smallest of the three parties, the PNP, meanwhile met a high-ranking Chinese envoy in Tokyo on Tuesday.

Chinese Vice Foreign Minister Wu Dawei met Shizuka Kamei, who told him that "It is important that the Japan-China relationship will make progress in a forward-looking manner," according to a PNP official.

Wu replied that "we are putting emphasis on the China-Japan relationship too," the PNP official said.

China said it would host a summit with the leaders of Japan and South Korea that would focus on cooperation between the three countries, but that no date had been finalised.

Japan's Asahi Shimbun daily, citing unnamed Chinese government sources, reported that the meeting would be held in the northern Chinese city of Tianjin on October 8.