Phil Mickelson and Ernie Els each sparked triumphs Friday at the storm-hit Presidents Cup but four matches were suspended by darkness as the potential for a Monday finish loomed.

At sunset, the United States led the Internationals 4 1/2-3 1/2 with each team ahead in two of the matches that will be finished Saturday morning before the start of five four-ball and five foursomes matches at Muirfield Village.

Reigning British Open champion Mickelson, a five-time major winner, and Keegan Bradley, the 2011 PGA Championship winner, defeated Australian Jason Day and Canada's Graham DeLaet 4 and 3.

"We played some of our best golf on the front nine," said Mickelson. "I love the energy, the excitement, the quirkiness he brings. We enjoy playing together. He brings out the best in me."

But the Internationals answered when South Africa's Els and Zimbabwe's Brendon de Jonge beat Hunter Mahan and Bill Haas 4 and 3.

"We both played well," Els said. "We had a lot of looks at birdies. We were 7-under when we finished. That's going to win most matches."

A severe thunderstorm dumped nearly an inch of rain on the course in about 90 minutes and halted play for two hours and 36 minutes, ensuring not all would finish.

"Everyone is sort of getting tired now," said Internationals captain Nick Price. "It's just the mental impact of sitting there, drying everything off and going back out to a wet course."

An 80 percent chance of thunderstorms is forecast on Sunday, when 12 final singles matches are planned.

"Monday is a consideration," said event director Steve Carman. "It's our intent to try and avoid that."

The Americans lead the biennial rivalry 7-1-1 after winning the past four in a row.

The Internationals have not won an alternate-shot session since 2005, dropping seven in a row to the Americans.

World number one Tiger Woods and Matt Kuchar were 3-up over South Africans Charl Schwartzel and Louis Oosthuizen after 12 holes while Steve Stricker and Jordan Spieth led South Africans Richard Sterne and Branden Grace 3-up with four holes to play.

World number two Adam Scott, the reigning Masters champion from Australia, and Japan's Hideki Matsuyama led major winners Jason Dufner and Zach Johnson 4-up after 11 holes while Aussie Marc Leishman and Argentina's Angel Cabrera led Brandt Snedeker and Webb Simpson 1-up after 13.

"It's going to be a long weekend, that's for sure," Scott said.

In the US win, Day sank a 12-foot birdie putt to win the first hole and only 15-foot putts by Bradley at the second and fourth to halve the holes kept the US duo close.

"They gave me more of a burst of energy watching them as if I had made them," Mickelson said. "That's when we really got going."

Mickelson responded with a 17-foot eagle putt to win the par-5 fifth, then hit an approach inches from the hole to set up a birdie to take the sixth.

Birdies at seven and eight stretched the US lead and just after play resumed, Day missed a par putt at 10 to fall 4-down. Bradley sank birdie putts at 11 and 12.

Bradley missed a 3-foot par putt to lose the 13th and his poor tee shot led to a bogey to drop the 14th, but Bradley sank a birdie putt at the par-5 15th to halve the hole and win the match.

"We just fed off each other," Bradley said.

Three birdies and an eagle in the first five holes put Els and de Jonge ahead and Els halved the ninth with a bunker chip-in birdie just before the storm.

A birdie at 11 put them 4-up and the Africans halved the rest to seal the victory.

"He's an unbelievable player," Els said of de Jonge. "He's coming into his own right now. He's an unbelievable ball striker with great heart."

"I've played nicely but don't let Ernie give me all the credit," de Jonge replied. "He gives me great confidence and is a calming influence out there. It's nice to play with a Hall of Famer who puts it in the middle of the fairway."

Woods and Kuchar birdied six of the first seven holes to seize command of their match.

"I made a couple of good putts to put the heat on those guys," Woods said. "We've still got our work cut out for us."