The US team staged a stirring late comeback to stay in the hunt at the Presidents Cup on Friday after the tournament appeared to be slipping away, with Tiger Woods hailing their "phenomenal" spirit.

The US went into the alternate shot or foursomes format on day two trailing 4-1, after Ernie Els' Internationals enjoyed their best start to the biennial matchplay event since 2005.

They ended it 6.5-3.5 behind after clawing back against Els' young unit, who had looked to be closing on the Internationals' first victory since their only title in 1998.

At one point the Internationals were in firm control, but Justin Thomas and Patrick Cantlay both drilled huge putts on the 18th to clinch narrow victories for a US team that desperately needed points, with playing-captain Woods leading wild celebrations.

The pulsating day ended with the points split -- two wins each and one tie.

With 30 points at stake over the week, the Internationals need another nine from Saturday's eight matches and the 12 singles on Sunday for a famous victory.

"At one point it looked pretty bleak, but the guys turned it around. They played phenomenal coming in," said Woods. "It was important for us to end the way we did and it totally changed the last hour.

"The energy has been there," he added. "These guys are all young and extremely excited about being a part of this team. I think more than anything, it's just getting a feel for this golf course. It is fast."

Despite Els' team throwing away late points, he was more than happy with their performance.

"They (the US) played good at the end there," said the South African.

"But hey, look at the record we've had in the foursomes the last 25 years and for us to come out 2 1/2, 2 1/2 in the session is like a win for us. We would have taken that at the start of the day."

The omens looked good for the Internationals in a heavyweight opening clash that pitted former world number one Dustin Johnson and Matt Kuchar against the experienced Louis Oosthuizen and Adam Scott.

They started well, clinching the opening hole. Oosthuizen then missed a simple putt to hand the US a two-up lead by the fifth, before the International pair began clicking to win the sixth and eighth.

Tiger Woods (L) and Justin Thomas celebrate winning their match on day two
Tiger Woods (L) and Justin Thomas celebrate winning their match on day two AFP / William WEST

They turned the screws as the crowd roared them on to win at the 11th, 13th and 14th and whip the dejected Americans 3 and 2.

Behind them Canada's Adam Hadwin gave his team a lead on the first hole after a beautiful approach shot from young Chilean Joaquin Niemann against Xander Schauffele and Cantlay.

In a see-sawing tie, the advantage kept changing hands before Cantlay stepped up to sink a massive putt on the last to get the US team on the scoreboard.

Inspired, Woods and Thomas, the only US pair to win on Thursday, matched the exploits.

Woods missed a birdie putt on the first but found his range and they raced two-up through five against Hideki Matsuyama and An Byeong-hun, before the Internationals incredibly won three in a row.

The tight match went to the wire where Thomas held his nerve to drain a long putt to secure the point, with Woods fist-pumping and hugging his teammate.

Patrick Reed was met with boos again after his penalty for improving his lie in the Bahamas last week.

He appeared unfazed, making a birdie on the first with partner Webb Simpson before Australia's Marc Leishman and impressive Mexican Abraham Ancer hit straight back on the second.

The Internationals then took charge, hitting the lead at the fifth and never relinquishing it to win 3 and 2, with Reed finally responding to barracking fans, cupping a hand to his ear and making a digging motion with his putter at the 11th.

Australian debutant Cameron Smith was rested on Thursday after calling Reed a cheat over the incident in the Bahamas, and he was greeted with cheers by the partisan crowd.

He sunk a monster birdie putt to put himself and partner Im Sung-jae one-up at the first against Gary Woodland and Rickie Fowler. It was a close affair until the 17th when the Americans levelled to claim a valuable half-point.