* PM Abe retains close allies in key posts
* Former economy minister Amari gets party post
* Abe expected to push for constitution reform
* Abe appoints one minister from rival's faction

Japanese Prime Minister Shinzo Abe kept key ministers in their posts in a cabinet reshuffle on Tuesday, including finance, trade and foreign affairs, while appointing just one woman to the new lineup.

Abe, who has made female empowerment a high-profile policy, tapped Satsuki Katayama, a conservative lawmaker and former finance official, as minister of regional revitalisation and gender equality, Chief Cabinet Secretary Yoshihide Suga said in announcing the cabinet.

Abe, who returned to office in December 2012 after a troubled 2006-2007 term as premier, was re-elected leader of his Liberal Democratic Party (LDP) last month, putting him on track to become Japan's longest-serving prime minister.

The reshuffle focused on stability as Abe prepares to push ahead with his controversial attempt to revise the post-war pacifist constitution, political experts said.

His allies Suga and Finance Minister Taro Aso were reappointed, as were Trade and Industry Minister Hiroshige Seko, Foreign Minister Taro Kono, and Economy Minister Toshimitsu Motegi, who handled tough trade talks with Washington.

‘He's appointed old friends and reliable allies and kept people in key portfolios to buy stability,’ said Jeffrey Kingston, director of Asian studies at Temple University's Japan campus.

Kingston said the appointment of just one female minister in a 19-member cabinet ‘exposes the empty grandstanding on 'Womenomics'‘. The previous cabinet had two female members.

Abe acknowledged that Japan lagged other nations in the number of women in its cabinet posts.

‘We must recognise that the ratio of women cabinet ministers is low compared to other countries, but Japan has just begun to create a society where women can be more active,’ he told a news conference.

‘I think we will steadily nurture people who can become cabinet ministers.’

Abe appointed one lawmaker - Justice Minister Takashi Yamashita - from the LDP faction led by former defence minister Shigeru Ishiba, whom he defeated in the LDP leadership race.

Abe chose Takeshi Iwaya, a former parliamentary vice defence minister, to replace Itsunori Onodera as defence minister. Iwaya was known recently for backing Japan's legalisation of casinos.

Close ally Akira Amari, a former economics minister who resigned to take responsibility for a funding scandal in 2016, was appointed LDP executive for election strategy ahead of critical upper house elections next year, party officials said.

But his immediate challenges are to manage fractious trade ties with Washington and keep an economic recovery on track.

Abe will order his new ministers to compile an extra budget, he told the news conference, adding that he wanted Aso to do his best for Japan to make a full exit from deflation.

Last week, Abe and US President Donald Trump agreed to open new talks on a two-way trade pact to keep Washington from raising tariffs on Japanese car exports for now, though Trump could revive the threat if progress is slow.

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