Gareth Davies has guided Wales to a nail-biting 23-13 victory over Fiji to pile the pressure on Pool A rivals Australia and England.
Even though there was no bonus, the win on Thursday was the third for Warren Gatland's Welsh team after beating Uruguay 54-9 and England 28-25.
It left them on top of the "Pool of Death" on 13 points ahead of Australia (9) and England (6).
Wales will be guaranteed one of the two qualifying spots for the quarter-finals along with Australia if the Wallabies beat England on Saturday.
But Fiji made it so hard for Wales at Cardiff's Millennium Stadium, the home side failing to convert overwhelming first-half domination of territory and possession into points.
The Pacific Islanders rallied impressively at scrum-time and in the loose, capitalising on very poor out-of-hand kicking by Wales.
"That was so tough," Wales captain Sam Warburton said.
"The first half, I was knackered."
"But we have got three wins out of three. If someone had told us that at the start of the campaign, we would have been quite happy."
Wales scored two first-half tries through Davies and Scott Baldwin, five-eighth Dan Biggar kicking two conversions and three penalties.
Ben Volavola kicked two penalties for Fiji after Wales scrum infringements, and, despite losing influential halfback Nikola Matawalu to injury and giant goal-kicking winger Nemani Nadolo to a ban, the side crossed for one try through Vereniki Goneva.
AFP