Japan's defence minister faces the sack, reports said Saturday, after a series of gaffes including describing the rape of a 12-year-old girl by three US servicemen as a "sexual orgy incident".

Yasuo Ichikawa, who has only been in office for four months, was censured by parliament's opposition-controlled upper house in December, as was consumer affairs minister Kenji Yamaoka, who backed an alleged pyramid sales firm.

Both men are expected to be removed in a cabinet reshuffle by Prime Minister Yoshihiko Noda, Jiji Press news agency and other media reported.

Noda, who took office in early September, is considering dismissing them in a bid to gain cooperation from the opposition to pass a budget and a package of tax and social reform bills through parliament, they said.

Ichikawa has committed or been linked to a series of gaffes that have offended the people of the island of Okinawa, reluctant hosts to a large US military presence.

One of his officials was dismissed after likening the government's foot-dragging on plans to relocate the US military base to forewarning a woman of the intention to rape her.

In 1995 three US servicemen raped a 12-year-old girl on Okinawa, a crime that galvanised islanders' resentment of the US presence.

Ichikawa claimed not to know the details of the rape, and at a press conference called it a "sexual orgy incident".

He also skipped a palace banquet in November in honour of visiting royals from Bhutan in favour of a political fundraiser he said was "more important".

As well as being admonished for alleged ties with shady business groups before he became consumer affairs minister, Yamaoka has come under fire over comments he made in a New Year address.

"I privately think the next biggest tsunami that will come soon may be the collapse of the euro," he said, remarks seen as belittling the victims of Japan's March 2011 earthquake and tsunami, which left 20,000 dead or missing.

Noda, the latest holder of Japan's revolving-door premiership, is expected to conduct the reshuffle possibly on Friday or in the following week, before parliament reopens in late January, the reports said.

The main opposition Liberal Democratic Party has threatened to boycott the legislature if the pair stay in place.

Jiji said Chief Cabinet Secretary Osamu Fujimura had told all ministers to make sure that they attend a cabinet meeting set for Friday, while economy minister Motohisa Furukawa had cancelled a January 11-15 visit to the US.

But the reshuffle could be delayed to early next month to coincide with the planned launch of a new government agency tasked with reconstructing areas devastated by the March disasters, the reports said.

Kyodo News agency said the reshuffle would be minor.

Possible candidates to succeed Ichikawa as defence minister include ruling-party lawmaker Yuichiro Hata, a son of former prime minister Tsutomu Hata, Kyodo said quoting anonymous sources.

In recent polls ratings for Noda's government have fallen to 30-40 percent from 50-60 percent soon after its launch, amid criticism over his handling of the nuclear crisis that followed the quake-tsunami and plans to raise taxes.