Australian golfer Adam Scott is urging his International team to regroup quickly after a United States clean sweep on the opening day of the Presidents Cup.

The US triumphed in all five four-ball matches at the Royal Montreal Golf Club for a commanding five points to none lead.

Scott and compatriot Min Woo Lee lost their match against Americans Colin Morikawa and Sahith Theegala, who prevailed one-up on Thursday's opening day.

Australia's Jason Day and Byeong-Hun An lost by the same margin to Tony Finau and Xander Schauffele on a grim day for the International team.

"We're now in a really tough spot but thankfully there's tomorrow … it's not over," Scott said.

"We're going to have to come out, fight really hard, find that gear, win a session and get going in the right direction.

"We have fought our whole careers to get into this team.

"We've faced many challenges as pro golfers — this is another one coming.

"It's obvious what we have to do … we just have to lift our level."

The Americans need to reach 15.5 points to retain the trophy in the biennial match play event pitting a 12-man US team against a line-up of International players from outside Europe.

Five foursomes matches will be contested on Friday with Day echoing the sentiment of his fellow Australian Scott.

"Unfortunately, we just didn't quite get it," Day said.

"The best players in the world had to birdie the last hole to beat us.

"That's why grinding it out is important. We have just got to kind of regroup and think about tomorrow."

World No.1 Scottie Scheffler and Russell Henley added to the US lead with a three-up win over South Korean duo Im Sung-jae and Tom Kim.

Patrick Cantlay and Sam Burns secured a two-up triumph over Japan's Hideki Matsuyama and Canada's Corey Conners moments before Keegan Bradley and Wyndham Clark earned a one-up victory over Canada's Taylor Pendrith and South Africa's Christiaan Bezuidenhout.

"I'm disappointed," Scott said.

"Min Woo and I could have won that match today, it's disappointing that we didn't do just a little bit better.

"I have a feeling the matches were closer than what the score indicates.

"Our guys are just going to have to lift a little bit, we're going to have to find another gear to beat a tough American team.

"The scoreline looks rough but I don't think there was that much difference in it today."

The US have held an opening-day lead in eight of the last nine Presidents Cups and are chasing a 10th consecutive triumph in the event.

AAP