Samoa cursed a disallowed try which denied them a third World Cup upset over Wales Sunday and rocked their tournament hopes - but insisted they could still reach the quarterfinals.

Captain Mahonri Schwalger said referee Alain Rolland's decision to rule out Maurie Faasavalu's effort for a double-movement was "pretty harsh" and may have changed the course of the game.

Flank Faasavalu shoved the ball over the tryline after an 18-phase assault through the forwards in the first half, but replays showed he had moved the ball over the line after being tackled just short.

Samoa finally scored after a similar attack on the stroke of half time and nearly pinched a late try with the same tactic, before being forced to settle for a 17-10 defeat.

"That was pretty harsh and it might have been the turning point of the game," Schwalger said. "There's some things you can't win and that's the way it goes. All we can do now is just move on."

It was Samoa's first World Cup loss to Wales after their stunning upsets in 1991 and 1999, and badly dented their hopes of qualifying from a tough Pool D also bracketing South Africa, Fiji and Namibia.

But Schwalger backed his team to pull off the mountainous task of beating Fiji as well as defending champions South Africa in their final two games.

"There were a few things where the referee was pretty harsh on us but that's the way it goes you win some, you lose some," Schwalger said. "We've still got a chance - if we win our next two games we'll be fine."

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

Assistant coach Brian McLean said Samoa could challenge South Africa but they needed to be more clinical, after dropping the ball just metres from an open line in the first half and missing tackles before Wales's only try.

"It's going to be really tough but they probably should have lost to Wales, and we gave Wales a bit of a fright. We think we can be competitive but it is a tough pool," McLean said.

"We need to be a little bit more accurate. We did some really good things but our own inaccuracies probably let us down more than anything else. We're creating the opportunities but our own inaccuracies are letting us down."

AFP