Solomone Kate scored 16 points for Tonga as they beat the Cook Islands 28-8 to book the final Pacific qualifying spot for the 2017 World Cup.
Kata's 16 points - two tries and four conversions - proved significant for the Mate Ma'a, who were expected to blow away their callow opponents in the winner-take-all showdown but only led by 12-8 at half-time at Campbelltown Stadium in Leumeah, New South Wales.
Jorge Taufua, Mahe Fonua and Peni Terepo also scored tries for Tonga, who have become the first team to claim one of the seven qualifying spots for the 2017 finals, which will be held in Australia, New Zealand and Papua New Guinea.
Charnze Nicoll-Klokstad and Wigan centre Anthony Gelling crossed the whitewash for the Cook Islands in the one-off qualifying match played at Campbelltown in Sydney on Saturday.