After completing a rare sweep of the morning foursomes, the Americans ended a sun-drenched day at Royal Montreal Golf Club leading the Internationals by 14-points to 7-1/2.
With 12 points up for grabs in Sunday's singles, holders the U.S. need only three more to claim the trophy for a fifth time.
Neither team has triumphed when coming from behind on the final day in the competition's previous six editions and the Americans are poised to taste their first victory on foreign soil.
" It's not over but things don't look too good," Internationals captain Gary Player told reporters. " The egg is not sunny-side up.
" The Americans are looking very, very good and we will really have to pull a rabbit out of the hat tomorrow."
Player has top-loaded his singles order with his strongest players to get blue points on the board early. The fourth match out pits world number one Tiger Woods against local favorite Mike Weir.
" It's just a matter of getting off to a good start, getting some momentum going, you can really feed off that," said Canadian left-hander Weir. " I've got my hands full for sure."
Reuters