Dustin Johnson threw down the gauntlet to his US Open rivals when he blasted a seven-under 63 to claim the halfway lead in the FedEx St Jude Classic at TPC Southwind in Memphis

The 2016 US Open champion mixed three birdies with two bogeys on the back nine before holing his second shot from 111 yards for an eagle two at the first en route to a homeward 29.

He leads by a shot on 10-under par from Ryan Blaum and Andrew Putnam, who both shot 64, with Seamus Power four strokes behind in a tie for seventh after a visit to water at his final hole saw him finish with a double bogey six for a 69.

It was a frustrating finish for the West Waterford man (31), who led overnight after a 65 and picked up birdies at the 11th, 12th and 13th to close to within two of the world No 2.

Even though he bogeyed the 15th, his sixth, he birdied the par-five 16th with a wedge to five feet, negotiated the trick 18th in par and then chipped in from behind the fifth for birdie to get within a shot of the lead on nine-under.

Playing late in the day, Power handed that shot back when he found rough at the next and then missed the ninth fairway to boot, finding water left of the green with his approach from 158 yards, leading to that costly late double bogey.

Shane Lowry recovered from his opening, two-over 72 by coming home in three-under on the front nine for a 67 to move up to tied 40th on one-under.

Playing partner Pádraig Harrington is a shot further back after a 72, making the level par cut on the mark as he bogeyed the fifth and ninth coming home.

Johnson is confident in his game, which bodes well for his US Open chances, cruising around in seven-under.

"It's never easy. But I feel like I am playing really well and I am swinging the club very well," said the American, who mixed three birdies with two bogeys on the back nine before scorching around the front nine in six-under 29.

The former world number one started for home with an eagle two, holing his second shot from 111 yards at TPC Southwind's 434-yard first.

He then birdied the second, third, sixth and ninth for his 63 and confessed that he's bursting with confidence as he counts down to Shinnecock Hills.

"I know if I can drive it in the fairway I am going to give myself a good look for birdie," said Johnson, who was one over for his round after four holes.

"I did that today - hit a lot of really great shots in there and had a lot of good looks at birdies."

With his power fade working like a dream, he feels in total control on a course that can be hugely punishing. 

"I feel like I am swinging good, so I have a lot of confidence in my swing," he said. 

"And here, because you have to hit a lot of fairways and you've got to trust it, and I feel like I am doing that really well right now."

On the European Tour, Derry’s Ruaidhri was the only Irishman to make the cut in the innovative Shot Clock Masters in Austria.

The Challenge Tour regular finished with eight straight pars for his second 73 on the trot to make the cut on the two-over-par limit.

Holywood Golf Club amateur Tom McKibbin (15) missed out by three shots after a 78 with Gavin Moynihan a shot further back after a forgettable 79.

As Nico Geyger, Henric Sturehed and Kristian Krogh Johannessen recorded the fastest round for the second day in succession — just three hours and 47 minutes —Finland’s Mikko Korhonen birdied shot a bogey-free 67 to lead by a shot on nine-under-par from Steve Webster and Justin Walters.

At the Challenge Tour’s KPMG Trophy in Belgium, Cormac Sharvin shot a four-under 67 to lie eight shots behind leaders David Law and Stuart Manley on five-under.

Tullamore's Stuart Grehan is a shot further back after an eagle at his 16th hole helped him shoot a second successive 69 to make the cut on the mark.

Neil O'Briain (71) and Stephen Grant (70) missed the four-under-par cut by two strokes with Dermot McElroy (73) and Jonathan Caldwell (72) well back on one-over and four-over respectively.