Warren Gatland’s side take on the Wallabies in a crunch Pool D clash which follows Wales’ opening 43-14 win over Georgia.
Head coach Gatland has named an unchanged side with Williams continuing at full-back. There is one change among the replacements with Owen Watkin replacing Leigh Halfpenny.
Williams said: “We had an OK win against Georgia. It was good to get that first game out of the way, get our first blow out, and get used to the conditions here.
“Training has gone really well this week and we are looking forward to the game now.
“I’ve played in a good couple of games against Australia and it has always been nip and tuck. We’ve worked hard to get where we are and hopefully that’ll take us into the game.”
Williams helped Wales to a crucial 9-6 victory over Australia when the two sides last met in November 2018 as fly-half Dan Biggar kicked a match-winning penalty.
Of their next encounter, Williams continued: “It’s going to be hot, that’s all I know. We have got a few tricks up our sleeve and as long as we stick to the process, I think we’ll go well on the weekend.
“Australia have tried a couple of changes to negate our kicking strategy. Dane Haylett-Petty at the back is really good in the air and Adam Ashley-Cooper has got years of experience – he’s world class.”
Gatland’s back-row of Aaron Wainwright, Justin Tipuric and Josh Navidi will take on the likes of Michael Hooper and David Pocock in what should be a thrilling battle.
Of the last 14 games between the two sides, the average points difference has been just seven and a similarly tight encounter is expected on Sunday.
“We’re on the biggest stage of them all here at the World Cup and it doesn’t matter who we play, we have to be at our best,” said Williams, who scored a try against Georgia.
“I’m pretty sure the boys are in a good place. It’s been a good week and we’re really ready to go.
“It’s hot and humid here and it could open up. If it does, then happy days.
“Last November was great. I’d played in a couple of games with Australia and we’d lost in the last play of the game. It was big, but the past is the past and now we’re looking to the future.”
Wales captain Alun Wyn Jones will make Welsh rugby history against Australia by winning his 130th cap. It means he will overtake the previous record of Gethin Jenkins who won 129 caps.
On Jones’ achievement, Williams said: “It’s incredible. I read something online that he’s been playing for Wales for 13 years. It’s incredible. I’ve been here for seven years and feel like I’ve been here for ages. He’s almost double me.
“He’s a great bloke and leads from the front. He speaks well and does his talking on the pitch as well.
“He’s a leader and I’m sure it will be a great occasion for him on Sunday. He seems quite calm at the moment. He doesn’t unleash the fury, not on me anyway! He’s the skipper so he can do what he wants!”
Australia have made four changes for Wales. Wing Reece Hodge is suspended, so Ashley-Cooper comes in to start at his fourth World Cup.
Haylett-Petty replaces Kurtley Beale at full-back and there are new half-backs in Will Genia and Bernard Foley.
