Ireland's Paul Dunne could become the first amateur winner of The Open since 1930 ©Getty Images

Irish Amateur Paul Dunne will go into the final round of The 144th Open tomorrow as the joint leader but American Jordan Spieth will start as the favourite after he finished his weather-affected third round only one shot off the lead. 

The 21-year-old American, bidding to become the first man to win the year's first three majors since Ben Hogan in 1953, appeared to be slipping out of contention in the early stages of his third round only to rally spectacularly and finish with a seven-birdie, six-under par 66 for an 11-under total. 

"I kind of just wanted to stay patient today, let them come to me, and once I figured out my putting, it did," the world number two Spieth, who hit three consecutive birdies at the 10th, 11th and 12th and then another at the 15th, said. 

"I can't speak for tomorrow given it's the last round, and if I have a chance coming down the stretch, if it creeps in, I'll embrace the opportunity."

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America's Jordan Spieth is seeking to become the first player since Ben Hogan in 1953 to win the first three majors of the year ©Getty Images

There will be a lot of support for Dunne, a 22-year-old from Greystones in County Wicklow, who came through final qualifying at Woburn, as he seeks to become the first amateur to win The Open since American Bobby Jones in 1930. 

Dunne is currently tied at the top on 12-under par 204 with Australian Jason Day and South Africa's 2010 Open champion Louis Oosthuizen after shooting 66. 

Dunne's three-round total of 204 broke the previous record for the lowest score by an amateur over the first 54 holes of The Open, set by Iain Pyman at Royal St George's in 1993, by six shots.

"I saw that I was tied for first on the 10th green and I said to my caddie how cool is it to leave The Open on Sunday, even if it's a different type of Sunday," Dunne, who attends the University of Alabama at Birmingham, said.

"The golf ball still does what you ask it to do, it's just there are more people watching and more cameras.

"I don't see why [an amateur could not win a major].

"I'm well capable of shooting the score that I need to win if everyone else doesn't play their best."

As an amateur, however, Dunne will not receive the £1.15 million ($1.80 million/€1.65 million) first prize should he win The Open.

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The Open at St Andrews is set to be one of the closest in the event's 144 history with 25 players all within five shots of each other ©Getty Images

Following the heavy rain on Friday (July 17) and the gales which made things so difficult yesterday, leading British officials to extend The Open until Monday for only the second time in its history, conditions were perfect today. 

That made it all the more surprising that American Dustin Johnson, the overnight leader and runner-up to Spieth at the US Open, collapsed to the day's second worst round, a miserable three-over 75.

Day, whose U.S. Open bid was scuppered by vertigo, made up five strokes during the day in a round of 67, as did Oosthuizen.

But the final round is on a knife-edge with 25 players separated by just five shots. 

"There are so many players who can still win this," Oosthuizen said.

"It's going to be I think one of the tightest Opens."

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