Marc Leishman likened the Royal Melbourne crowd to climbing an alpine pass in the Tour de France as he and "Aussie Abe" Ancer pulled off a crucial Presidents Cup comeback today.

Defending a four-point lead against a hard-charging American team, the Internationals were faced with the very real possibility of having that lead vanish in one quick and damaging afternoon foursomes session.

But just as the American team had rallied late a day earlier to stem the bleeding, the Australia-Mexico combination conjured a near miracle to thwart impending disaster.

As it was, two epic halved matches slashed the Internationals' lead to two points ... but that was a pipedream for Ernie Els' men for much of a the afternoon.

Rickie Fowler and Justin Thomas picked up where they left off from a dominant morning fourball win to have Leishman and Ancer on the ropes in the afternoon.

Two early American birdies and a series of misfired putts by Leishman in particular had the home team in a 5-down hole as early as the seventh.

That score hadn't changed until Leishman cashed in on a great Ancer pitch and drilled the team's first birdie on the 11th green.

The 2018 Australian Open champ returned the favour after a brilliant Leishman approach to the 12th and suddenly, from nowhere, there was a pulse at 3-down.

But having barely missed a shot until that point, there seemed no panic from the American duo who steadied to have the hosts on the ropes.

Despite a birdie bomb from Ancer on the long 15th, the International team could scarcely have conceived of the drama ahead.

After Thomas' first putt had come up 2m short, Fowler was shocked when his par putt to win the match lipped out and the match went to the 17th, where the roles were reversed and Thomas missed from 3m to cede the hole and send the crowd into a frenzy.

By now the Americans were anything but bulletproof and when Thomas ripped his drive through the fairway and into the left trees, their goose was cooked.

Fowler bunted the ball back into play, but Leishman drilled a 9-iron to 2m and the deal was as good as done.

Thomas' approach to almost 20m above the hole left his mate with a nearly impossible par putt and while Fowler made a great fist of it, joint concessions as it passed the hole gave the hosts the most unlikely half-point.

"That absolutely felt like a win," Leishman beamed.

"That's probably as good as I've felt on a golf course, and I only halved the match.

"Walking to the 18th through that crowd felt like you were like riding up the hills in the tour de france, the crowd was amazing.

"I've never felt anything like that before in my life."

Ancer continues to impress and thrive in Australia.

He won in Sydney last year, was runner-up for Mexico in the World Cup the following week and now has 3.5 of a possible four points against the vaunted Americans.

"I never really lost hope," Ancer said.

"I've come back from 5-down before, and I just told Marc, `Hey, we're still in it, let's just keep pushing and see what happens'. And we did.

"Once we started making putts there and seeing the ball go in - I think even 11, 12, obviously were huge, seeing some putts go in, hitting some good shots, (I thought) we were back in this.

"We knew we needed to make something happen, and we did it. It was really special. Obviously it wasn't going to be easy. We knew we needed some help and we needed to execute to perfection, and thankfully we did.

"It was just an unbelievable experience, something I'll never forget.

"The emotions were high, the people were amazing, we're stoked."

Korean Ben An and Chilean Joaquin Niemann also fought a classic contest with Matt Kuchar and Tony Finau that ended in a tense tie as An, so steady with the putter throughout, pulled a 2m birdie try on the last.

But the Americans did make ground courtesy of Xander Schauffele and Patrick Cantlay against Cam Smith and Sungjae Im, and also Dustin Johnson with Gary Woodland against Louis Oosthuizen and Adam Scott.

Scott paid tribute to the fighting qualities of his teammates in a press conference alongside Leishman and Ancer.

"It was a big last hour for us today," Scott said.

"I certainly feel like it showed our intentions as a team. There's a lot of heart sitting here next to me.

"That was huge for us - and also Ben and Joaquin Niemann digging deep and finding a halve.

"It goes a long, long way, the half-points. The scoreline is really good for us, considering what it was looking like with a couple hours to go.

"But tomorrow is another day. We're in the middle of a fight and we're all going to be up for it."

SUNDAY'S SINGLES DRAW (International v USA)

Abraham Ancer v Tiger Woods 10.02am

Hideki Matsuyama v Tony Finau 10.13am

C.T. Pan v Patrick Reed 10.24am

Haotong Li v Dustin Johnson 10.35am

Adam Hadwin v Bryson DeChambeau 10.46am

Sungjae Im v Gary Woodland 10.57am

Joaquin Niemann v Patrick Cantlay 11.08am

Adam Scott v Xander Schauffele 11.19am

Ben An v Webb Simpson 11.30am

Cameron Smith v Justin Thomas 11.41am

Louis Oosthuizen v Matt Kuchar 11.52am

Marc Leishman v Rickie Fowler 12.03pm