PERTH, 25 Oct, 2014 (AFP) - Olesen fired a five-under 67 in Saturday's third round and leads the European Tour co-sanctioned tournament at 16-under 200 from South Korean Sihwan Kim.
"It's been a couple of years since I won, so definitely I'll feel the nerves," said Olesen, whose only main tour success came at the 2012 Sicilian Open.
"I've been in contention in big tournaments and I know how it feels," added Olesen, who finished sixth at The Masters in 2013.
Despite shooting six birdies and just one bogey, only his second for the tournament, Olesen said he wasn't feeling comfortable with his game.
"I tried to go out there and be aggressive like I did the first two days, but I didn't have the game today," he said.
"It didn't feel good, I was struggling out there. I made some great up and downs to keep it going."
Kim, who carded a three-under 69 on Saturday, is aiming to be the second South Korean to win the Perth International after Jin Jeong won the title last year.
"It's quite funny how last year Jin didn't have any status anywhere and ends up winning this tournament and he has status on the European Tour," said Kim, who needs to finish outright second or win to retain his European Tour card.
England's James Morrison is in third place, four strokes behind Olesen after carding a three-under 69.
American Peter Uihlein was the big mover on Saturday, firing a seven-under 65 to move into outright fourth at 11 under 205.
Pre-tournament favourites Charl Schwartzel (nine under) and Frenchman Victor Dubuisson (eight under) have plenty to do in the final round.
American Jason Dufner, playing his first tournament since recovering from a serious neck injury, finished at seven under 209.
Second-round leader Peter Whiteford (nine under) fell off the pace after shooting a three-over 75 on Saturday.
Leading scores after the third round of the Perth International at Lake Karrinyup (par-72) in Perth on Saturday (Australian unless stated):
200 - Thorbjorn Olesen (DEN) 64-69-67
203 - Sihwan Kim (KOR) 66-68-69
204 - James Morrison (ENG) 72-63-69
205 - Peter Uihlein (USA) 69-71-65
206 - Richard Green 68-68-70, David Drysdale (SCO) 67-68-71
207 - Mark Foster (ENG) 67-73-67, Lucas Bjerregaard (DEN) 71-70-66, Gary Stal (FRA) 69-71-67, Stephen Dartnall 68-71-68, Charl Schwartzel (RSA) 68-69-70, Peter Whiteford (SCO) 66-66-75
208 - Mikko Korhonen (FIN) 71-70-67, Jason Norris 71-69-68, Andrea Pavan (ITA) 71-70-67, Nathan Green 71-71-66, JB Hansen (DEN) 71-68-69, Victor Dubuisson (FRA) 71-67-70
209 - Jason Dufner (USA) 70-70-69, Nick Gillespie (NZL) 71-71-67, Marcus Fraser 68-70-71
Selected scores:
210 - Jamie McLeary (SCO) 70-71-69, Richard Bland (ENG) 68-72-70, Matthew Nixon (ENG) 70-71-69
212 - Gregory Bourdy (FRA) 69-72-71, Julien Quesne (FRA) 67-73-72, Magnus A Carlsson (SWE) 67-76-69, Carlos Del Moral (ESP) 71-72-69
213 - Stuart Manley (WAL) 73-68-72, Jack Doherty (SCO) 69-72-72, Kevin Phelan (IRL) 72-69-72, Damien McGrane (IRL) 70-70-73, James Heath (ENG) 72-71-70
214 - John Parry (ENG) 69-72-73, Soren Kjeldsen (DEN) 69-71-74, Daan Huizing (NED) 68-73-73, Ricardo Gonzalez (ARG) 68-74-72, Scott Jamieson (SCO) 69-74-71, Simon Wakefield (ENG) 72-67-75, Soren Hansen (DEN) 72-71-71
216 - Tom Lewis (ENG) 66-74-76, Nacho Elvira (ESP) 71-71-74
217 - Craig Lee (SCO) 73-69-75, Roope Kakko (FIN) 72-71-74