Harrington carded a 68 at windswept Carnoustie to move within a shot of the lead held by Wales' Bradley Dredge, who recorded a 71 at Kingsbarns.

Former American Walker Cup player Edward Loar held third place on nine under with Ernie Els and Vijay Singh a shot further back.

The first prize of £427,000 could lift Harrington from fifth to second on the money list and, depending on the performance of current number one Paul Casey, to within around £70,000 of his Ryder Cup team-mate with two events remaining.

"There is still a long way to go, " said Harrington.

"Tomorrow is going to be another tough day at St Andrews and Bradley is obviously playing very well.

"I knew I was a long way behind in the Order of Merit but with three events still to go I set myself a goal of trying to get into the mix.

"After the Ryder Cup it would be very easy to sit back and it's a bit of a downer after you win something like that, so I was trying to motivate myself.

"I knew it was a very long shot, and it still is, but it's something I'm using as a motivational tool."

The Mallorca Classic from October 19-22 and seasonending Volvo Masters the following week will decide who succeeds Colin Montgomerie as European number one.

Casey and his nearest challenger, Ryder Cup team-mate David Howell, are definitely not playing in Spain, but Harrington admitted he was seriously thinking about it.

"I'm asking about it so that tells you, " he added. "We'll have to see how things go on Sunday and then I'll be able to tell you my plans."

Harrington won this title in 2002 following a play-off with Eduardo Romero and also took the team prize with amateur partner JP McManus.

They lead again on 25 under this year and despite his second round 69 at St Andrews taking almost six hours on Friday, Harrington feels being part of a team is actually helping his game.

"The last time I won in 2002 we won the team event as well and it's definitely better for your individual golf to be part of a team, " added the Dubliner, who surprisingly won just half a point in Europe's Ryder Cup triumph at the K Club.

"I lost a bit of patience in the middle of my round but I focused more on the team score and that gave me a lift."

Casey currently enjoys a lead of £80,000 over Howell and was in with a chance of clinching the title here when he led after an opening round of 63 at Kingsbarns.

However, the 29-year-old drove out of bounds on the 18th at St Andrews in a 74 on Friday and returned a 73 at Carnoustie to lie five under par, eight shots off the lead.

Howell birdied three of his last five holes at Carnoustie to card a highly creditable 70, but still missed the cut by some distance as he struggled with the recurrence of a shoulder injury.

"I think it was an event too far for me, " the Swindon golfer said. "But it looks like there is still all to play for and I must try and get myself fit."

Montgomerie felt he had played himself back into the event after a 67 at St Andrews on Friday but missed the cut after a disastrous 80 at Carnoustie, where he holds the course record of 64.

But the 43-year-old Scot looked like still being back in action at St Andrews on Sunday to accompany amateur playing partner Michael Douglas in the team event.

The pro-am event sees each of the 168 professionals teamed up with an amateur partner.

The teams play one round at each of the courses over the first three days before the top 60 professionals and those tied for 60th place, together with the top 20 teams, compete in Sunday's final round at St Andrews.