Samoa needed at least a bonus point to take the second qualifying spot, but Fiji scored five tries one to retain the Pacific Nations Cup title and finish the two-year Oceania qualifying series unbeaten.
Tonga complete the Rugby World Cup’s hardest-looking pool, beside England, France, Argentina, and the United States.
The likelihood is that Samoa will now end up alongside Scotland, Ireland, hosts Japan and a European qualifier in Pool A in 2019. The Scots and the Samoans had a titanic battle at the last World Cup in 2015, with Scotland eventually winning 36-33 at St James’ Park in Newcastle.
Fiji qualified last weekend after beating Tonga 14-10, and slotted into Pool D at the World Cup with Australia, Wales, Georgia, and an Americas qualifier, either Canada or Uruguay.
Samoa, who have competed in every Rugby World Cup since 1991, now face a repechage match against the winner of Czech Republic or Portugal versus the second-place team in the 2018 Rugby Europe Championship.
Fiji’s fourth win in a row continued a fine run of form in June and July internationals in which they accounted for Scotland and Italy.
The Fijians took an early lead with the first try of scrum-half Henry Seniloli’s hat trick, created by a pass from fly-half Ben Volavola which allowed an inside break from Akipusi Qera. Seniloli was rewarded in all three tries for his outstanding supporting play, staying on the shoulder of full-back Timoci Nagusa to score his first. Samoa equalised through captain David Lemi when scrum-half Kahn Fotuali’i caught Fiji napping with a quick tapped penalty.
Seniloli scored his second when winger Vereniki Goneva made a break down the right flank.
Fly-half Tusi Pisi missed his first two shots at goal but kicked three in a row to give Samoa a 16-14 lead at half-time, when it began raining.
Seniloli completed his hat trick immediately after half-time, finishing a move in which Nagusa was again prominent.
Centre Jale Vatubua ran off a pass from Nagusa and replacement Api Ratuniyarawa crashed over from close range six minutes from full-time. Volavola kicked six goals from six attempts, converting all of Fiji’s tries and a penalty from 55 metres.
“It was a great win and our bench was great and it showed in the second half,” Fiji coach John McKee said. “This is a talented group and we have some younger talent emerging also. I believe this squad can improve further and our aim will be to make the quarter-finals in 2019.”