The lightly regarded American duo shot a 6-under 66 on Saturday, giving them a one-stroke lead over France (62) and Scotland (66) going into Sunday's final round at the Mission Hills Golf Club in southern China.
They are 20-under 196 and have led after all three rounds.
Scores dipped on a warm, sun-drenched Saturday with teams playing the easier fourballs (better-ball) format. Sunday will be tougher playing foursomes (alternate-shot) in what is still a stroke-play event.
South Africa (66) and England (67) were two strokes off the lead. Argentina (64), the Netherlands (65) and Germany (66) were three behind.
Weekley and Slocum said they struggled all day with firm greens, tough pin placements and a swirling wind. In addition, neither made many putts. The exception was Weekley's eagle 3 on No. 3, where he hit a 4-iron to 15 feet and then dropped the uphill putt.
"It was just a tough day overall, it was a grind out there," Weekley said. "It wasn't like the first day when we hit it in there close and made some putts."
Said Slocum: "We survived with both of us not playing our best golf. So we have to feel a little fortunate."
After jousting with France for the lead, the United States moved to 20 under for the tournament
- and a one-stroke lead over the French - with Slocum's birdie on No. 13.
Weekley was chosen to play in the event after 13 other higher ranked Americans players declined. He then picked Florida high school friend Slocum as his partner. Both players have already won more than $2 million this season, and they'll each get $800,000 if they clinch victory here.