Donald will become world number one if he can win in South Carolina
-11 L Donald (Eng) -10 J Furyk (US) -9 B de Jonge (Zim), S Verplank (US) -8 R Barnes (US), T Gainey (US), J Day (Aus) Selected others: -6 G Williams (US) -5 C Villegas (Col) -4 M Kuchar (US) -3 Ian Poulter (Eng) -2 G McDowell (NI)
Luke Donald remains on course to become the new world number one as he maintained his one-shot lead after the third round of The Heritage event.
Donald, 33, shot a steady round of 70 and still leads the US PGA event from defending champion Jim Furyk (69).
Zimbabwe's Brendon de Jonge (66) and Scott Verplank (67) of the US lead the chasing pack on nine under par.
Donald will succeed Germany's Martin Kaymer as the top-ranked player if he can clinch victory in South Carolina.
With Kaymer taking the week off and fellow Englishman Lee Westwood playing in the
which carries fewer ranking points, victory would move Donald top of the rankings.
You have to go out there and try to win it, make some birdies and not try to hold on to that lead
Should he do so, the
WGC Match Play champion
will become the fourth world number one in less than six months.
"I have an opportunity to go out there and win, and if I do, then I know what's going to happen," he said.
Asked about his tactics for the final round on Sunday, Donald added: "It's pretty bunched behind me... so with just a one-shot lead you can't play protective golf.
"You have to go out there and try to win it, make some birdies and not try to hold on to that lead. I don't know if it's going to be windy again but the course is only getting harder and faster."
The world number three began the day with a one-shot lead but things quickly turned sour with a double-bogey on the second.
He birdied the fifth and seventh to recover but needed to dig deep again - this time via a birdie on the ninth - to rescue par at the turn after a bogey on the eight.
Birdies on the third and fifth allowed Furyk to pull level, joining Donald at 10 under for the tournament, before the Englishman re-established his one-shot advantage with a birdie at the 16th.
"It was tougher today, the wind was more of a factor and the greens are getting firmer and crustier," said Donald. "And I was pleased with bringing it back after that slow start."
American pair Ricky Barnes (67) and Tommy Gainey (67) and Australia's Jason Day (71) are three shots off the lead at Hilton Head Island.
Britons Graeme McDowell and Ian Poulter carded disappointing scores of 74 and 75 respectively to slip down the leaderboard.