With the Rugby World Cup just six weeks away, Japan will look to put the finishing touches on its preparations for the global showpiece against the United States in the Pacific Nations Cup in Suva, Fiji, on Saturday.

With both sides winning their first two games, Saturday's clash will determine the winner of the competition, which Japan won outright in 2011 and shared the trophy with Samoa in 2014.

Jamie Joseph's side scored a combined 10 tries and 75 points in wins over Fiji and Tonga over the last two weeks, putting its Pacific Island opponents to the sword with the kind of attacking rugby it hopes to reproduce at the World Cup, which it will hosts, starting Sept. 20.

"We are doing very well with our preparations for the World Cup," Brave Blossoms captain Michael Leitch said after arriving in the Fijian capital earlier this week.

"We have been together (in camp) since February ... we last won the Pacific Nations Cup in 2011 and if we win this game it will be after eight years.

"But the bigger picture is to win in the World Cup so this is part of the process," added Leitch, who returned to the starting lineup against Tonga last weekend after shaking off a groin injury.

Joseph, who missed the win over Tonga in Higashiosaka, Osaka Prefecture, due to the death of his mother, has rung the changes for Saturday's match.

The front row remains intact but Leitch is the only other forward to keep his place, with Pieter Labuschagne and Henrik Tui joining him in the back row.

Uwe Helu and James Moore replace Luke Thompson and Wimpie van der Welt in the locks.

Fumiaki Tanaka returns at scrumhalf after missing the opening two games with injury, while Yu Tamura continues at flyhalf, meaning he is the only No. 10 to get game time during the tournament.

Kenki Fukuoka, who scored against both Fiji and Tonga, starts on the wing in place of Lomano Lemeki.

The United States heads into Saturday's clash looking for its first Pacific Nations Cup title, having rejoined the competition this year after a three-year absence.

The Eagles thrashed Canada in Colorado in their opening game before edging Samoa 13-10 with a last-minute AJ MacGinty penalty last weekend.

Coach Gary Gold has made eight changes from that game, including the selection of an all-new back row.

Jamason Fa'anana Schultz makes his debut at No. 8 alongside Malon Al-Jiboori and Hanco Germishuy.

MacGinty, who scored all of the United States 19 points against Samoa, continues at No. 10 and is partnered by the experienced Shaun Davies, who comes in for Ruben de Haas at scrumhalf.

Japan defeated the United States 28-18 during their last meeting at the 2015 Rugby World Cup in England.

While Japan has improved its set-play over the previous matches, Leitch said the team is heading into a difficult challenge against the Americans, a match that can be an important test ahead of the World Cup opener against Russia.

"I think (the U.S.) are the strongest team at this tournament," Leitch said. "They are largely built, similar to the Russian team," he said. "I want it to be a match in which we can demonstrate our absolute best performance."

As part of Saturday's doubleheader, Fiji faces Samoa afterward.