PERTH, Australia, Oct 20, 2012 (AFP) - World number 24 Van Pelt holed a 15-metre putt from the back tier of the 18th green at the end of the day to grab a one shot lead over world number 10 Dufner at the US$2 million tournament at Lake Karrinyup.
He said he was pleased to end the day with momentum, adding: "It was just nice to finish with a birdie like that and hopefully take that into tomorrow."
Both Van Pelt and Dufner had third round 67's around the hilly par 72 layout with its treacherous undulating greens.
Twenty-year-old Grillo, seeking the first win of his short professional career, had four bogeys on the back nine for a disappointing 73 which left him two from the leader.
Van Pelt, 12 under par for three rounds on 204, was full of praise for Grillo who led on the first two days.
"He played a lot better than his score today," he said.
"He probably had five or six putts that looked like they were going to go in that just hit the edge, and that's just golf. Some days they go in and some days they hit the edge."
Grillo, an outstanding amateur who played for his country when he was only 14, remained upbeat about his chances of winning the tournament, which is co-sanctioned by the PGA Tour of Australasia and the European Tour.
He went to Australia to bolster his ranking (113) on the European Tour where he was in danger of losing his card in his rookie year.
"I have a good chance tomorrow," Grillo said. "I'm playing in the group in front of the last tomorrow. All of the people are going to be with them and they are going to have the pressure."
Van Pelt said the key to his score so far had been the four par fives which he played in 10 under par.
The American admitted his 15-metre putt at the last was a great "momentum builder" to take into the last day.
"Once in a while a hole just gets in the way," he said.
Van Pelt sees Dufner as his main rival.
"Jason is a great player," he said. "Grillo is playing well and he's probably going to come out and probably shoot a low one tomorrow.:
He added: "You've got to drive the ball straight and then put the ball in position on the greens, because they have a lot of slope and they are getting firm and they are getting fast."
Dufner also likes his winning chances.
"It was a nice day to get a good score and move up and have a realistic chance of not having to do anything crazy tomorrow and being in contention to try to win the tournament," he said.
But he said the course has a tough finish.
"I'll play conservatively on the first nine, maybe even 12 holes, and depending on where everyone else is might become a bit more aggressive," he said.
Scores after the third round of the $Aus2 million ($2.04 million) EPGA-sanctioned Perth International at Lake Karrinyup (par-72) in Perth on Saturday (Australia unless stated):
204 - Bo Van Pelt (USA) 70-67-67
205 - Jason Dufner (USA) 71-67-67
206 - Emiliano Grillo (ARG) 66-67-73
209 - David Howell (ENG) 71-68-70, Alejandro Canizares (ESP) 65-73-71
210 - Steve Jones 71-71-68, Greg Chalmers 68-73-69, Michael Hendry (NZL) 65-73-72
211 - Andre Stolz 70-73-68, Rhys Davies (WAL) 68-72-71
212 - Ignacio Garrido (ESP) 74-71-67, Scott Jamieson (SCO) 72-71-69, Edouard Dubois (FRA) 71-71-70, Mark Brown (NZL) 71-69-72, Robert Coles (ENG) 71-68-73
213 - David McKendrick 72-71-70, Paul Casey (ENG) 67-75-71, Knut Borsheim (NOR) 70-71-72, Ashley Hall 68-72-73, Stephen Dartnall 72-67-74, Peter Cooke 73-66-74, Jason Scrivener 68-69-76
Selected scores:
215 - Edoardo Molinari (ITA) 71-72-72, Sam Little (ENG) 72-71-72, Thomas Petersson (SWE) 70-72-73, Richard Bland (ENG) 70-69-76
216 - Oliver Wilson (ENG) 73-73-70
217 - Steve Webster (ENG) 72-73-72, Jamie Moul (ENG) 70-75-72, Craig Lee (SCO) 70-70-77
219 - Tommy Fleetwood (ENG) 75-70-74, Federico Colombo (ITA) 71-74-74, Matthew Baldwin (ENG) 74-71-74, Alastair Forsyth (SCO) 70-70-79
220 - Thomas Norret (DEN) 72-74-74, Mikael Lundberg (SWE) 75-71-74, Jin Jeong (KOR) 70-72-78, Andrew Johnston (ENG) 67-73-80