Momentum is usually easily defined; not so at this Presidents Cup after an epic day two at Royal Melbourne. For the second consecutive day, the International underdogs held their own and were full value for a 6.5-3.5 lead that represents the first time the team has led after day two since 2005.

But the big question of momentum came with the last hour of a frenetic day of foursomes action.

The Internationals had been down in a couple of matches early, but by the time the lead group of Adam Scott and Louis Oosthuizen caught fire and roared past Dustin Johnson and Matt Kuchar early on the back nine, the home team led in four matches and was square in the other.

Cheeky suggestions of a second session sweep were brazenly mooted by some fans daring to dream for the first time in a long time in what has been a largely lopsided competition for several editions.

Scott and Oosthuizen saluted, then Marc Leishman and “Aussie Abe” Ancer stretched the three-point opening day lead out to five when they eased past Webb Simpson and Patrick Reed 3&2.

And that’s when the remaining Americans on course seemed to flick the switch.

Rickie Fowler’s laser approach to 15 gave he and US Open champ Gary Woodland a lifeline almost at the same time as Canadian Adam Hadwin let slip a golden opportunity to put the Internationals dormie 1-up on 17 when his birdie try finished agonisingly short.

Rising Americans Patrick Cantlay and Xander Schauffele seized the opportunity in that match and when the former knocked in a closing birdie, he stemmed the bleeding for the visitors.

As he had on day one, Tiger Woods continued to lead with distinction. One of three US pairs to back it up on Friday, Woods and Justin Thomas were 2-up through four holes but Hideki Matsuyama’s putting kept he and Ben An alive.

A birdie at the driveable par-4 11th put the Asian duo ahead but they could only manage fours on each of the final seven holes.

With scores level coming up 18, Woods rifled his approach at the flag, leaving Thomas a slick 4m putt for an unlikely victory.

Roaring the words “Love me some me” – in honour of an NFL star Terrell Owens video he’d watched in the team bus en route to Royal Melbourne this morning – Thomas did his part and suddenly the tension was palpable.

Fowler took advantage of a huge break on the 16th in the final match against Sungjae Im and Aussie debutant Cameron Smith. Woodland’s drive flared right into the hospitality marquees, but rebounded into the middle of the fairway and his partner knocked it in tight for a rare birdie on the course’s traditional and brutal closing hole.

Fowler then cashed in on a great Woodland approach on 17 and suddenly, seemingly from nowhere, the Americans had a chance to snatch the session back.

Smith played Im into about 4m with a great approach that set up one last chance for the International team, but the Korean’s putt slid by, leaving Fowler a 1.5m curler which he duly knocked in for par to halve the hole and match.

It was a fitting end to a memorable day that had roared to life when Smith chipped in on the first and then ferreted another birdie from off the back of the third green to get the home fans pumping.

It left the margin precisely as it had been 24 hours earlier and both teams clamouring for mental superiority.

Woods said the final hour had been enormous for his team.

“At one point … it looked pretty bleak, but the guys turned it around.,” Woods said.

“They played phenomenal (golf) coming in. It was important for us to end the way we did and it totally changed (momentum).”

Leishman, for one, would not hear of the Americans’ claim.

“To be three points ahead after two sessions, one of which is foursomes, and we have struggled with it at all the Presidents Cups (I’ve) been involved with, yeah, (I’d take that position) for sure,” he said.

“I mean, any lead against them is good, but a three-point lead is even better.

“But there's still a lot of points to play for. We need to keep doing what we're doing and keep improving because we know their jet-lag is going to start wearing off, and I'm sure they will start firing up. We need to be ready for it.”

Woods opted to rest himself from Saturday’s early fourball session when the teams were formalised after play, confirming his pre-tournament promise not to play 36 holes in a day. Thomas will instead be paired with Fowler against Leishman and China’s Haotong Li, who will make his first appearance when play starts at 7.02am (AEST)

SATURDAY FOURBALL MATCHES (International v USA, time

Marc Leishman and Haotong Li v Justin Thomas and Rickie Fowler, 7.02am

Sungjae Im and Abraham Ancer v Xander Schauffele and Patrick Cantlay, 7.16am

Hideki Matsuyama and C.T. Pan v Patrick Reed and Webb Simpson, 7.30am

Adam Scott and Ben An v Matt Kuchar and Tony Finau, 7.44am