Wales shattered their 20-year jinx against World Cup bogey side Samoa on Sunday with a tense 17-10 win to keep their tournament hopes alive.

Veteran wing Shane Williams scampered over deep into the second half to secure the vital win which buried the ghosts of major upsets in 1991 and 1999 and put them on course for the quarterfinals.

Samoa edged a scrappy first half 10-6 but the Welsh backline came to life after the break and were rewarded with Williams's 67th-minute try - his 55th Test try and eighth in the World Cup, which is a record for Wales.

The win, following Wales's 16-17 opening loss to defending champions South Africa, puts them in the box seat to qualify second from Pool D with a likely quarterfinal against Six Nations rivals Ireland.

"We knew today was a must-win game," said coach Warren Gatland. "Forget about the performance, we just knew we had to win. That's why I'm so proud of the boys: under a bit of pressure, they just dug deep."

Samoa were left to rue referee Alain Rolland's decision to rule out Maurie Faasavalu's firs -half score for a double-movement as they face remaining fixtures against Fiji and South Africa.

"We're still there - I've got belief in my team," said captain Mahonri Schwalger. "My team will make the quarterfinals, if we concentrate on the next two games."

Wales coach Warren Gatland led the praise for Williams, who he believes still has pace to burn and lightning feet at the age of 34, remained a potent attacking threat in what is set to be his third and final World Cup.

Williams now holds Wales' try-scoring record with his eight try at a World Cup, breaking the record of seven held jointly by Ieuan Evans and Gareth Thomas.

"It's great to see him score another try. I thought he looked very, very dangerous on attack and I thought he was close on two or three occasions when he could have gone through and opened up the game," Gatland said.

"I thought he worked hard... It was great to see Shane working hard and finishing that try off."

Jonathan Davies said the "fantastic" Williams, who is the oldest player in Wales's squad, had taken on a mentoring role in an outfit packed with youthful players.

"He is the senior member but he's been around a lot and he's got a lot of experience," said Davies, 23.

"He is a bit of a calming influence on us all. He's been there and he's done it he makes sure that we're calling the right calls.

"I know he's out on the wing but we're all talking together and he's a massive part of the background.

"He's kept himself in great shape and he's a true professional."

AFP