Japan international Amanaki Mafi will stand trial in a New Zealand court next year for an assault charge, allowing him to play at the Rugby World Cup.

World Cup hosts Japan will play Ireland on 28 September in Shizuoka.

The 29-year-old Mafi was charged with intent to injure following an altercation with former Melbourne Rebels team mate Lopeti Timani in Dunedin in July last year.

The incident occurred after the pair had spent the night drinking with each other following the Rebels' Super Rugby match against the Otago Highlanders. Mafi, who spent the night in custody following the incident, had pled not guilty.

He will face trial on 27 January, 2020 at the Dunedin District Court, Judge Michael Crosbie said.

"It's not rugby season and the World Cup's over," the Otago Daily Times quoted Crosbie as saying in setting the date of the trial, which is expected to last three to four days.

The newspaper said the case had been called several times but finding a date for the trial had been a problem with Mafi living in Japan and Timani in France, while the World Cup was also an issue.

Both players were fined A$15,000 by the Rebels after the incident for breaching team protocols. They both left for new clubs at the end of the 2018 season.

Mafi was called into the extended Japan training squad for the Rugby World Cup, which starts in Tokyo in five weeks, despite his legal problems and played in the recent Pacific Nations Cup tournament.