There are growing calls within Japan's ruling party for Defence Minister Yasuo Ichikawa to resign before a censure motion next week over a string of gaffes that threaten the relocation of a U.S. military base, Japanese newspapers reported on Saturday.

Ichikawa should resign either before or shortly after the non-binding but embarrassing censure motion passes to limit damage to a cabinet launched only three months ago, several Japanese newspapers reported, citing senior ruling Democratic Party members.

If Ichikawa does resign, that could embolden the opposition and make it more difficult for Prime Minister Yoshihiko Noda to seek broad support to double the sales tax to 10 percent, change the welfare system and compile next fiscal year's budget.

A senior defence ministry official last week likened plans to relocate an airbase in the southern island of Okinawa to a rape, sparking anger and prompting opposition parties to agree on submitting a censure motion against Ichikawa to the opposition-controlled upper house of parliament.

The motion is likely to pass, Japanese media said.

Ichikawa is also under attack after he told parliament last week he did not know the details of a 1995 Okinawa rape case, in which a 12-year-old girl was assaulted by three U.S. servicemen, stoking anti-U.S. base sentiment on the island and shaking Japan's security alliance with the United States.

(Reporting by Stanley White; Editing by Yoko Nishikawa)