Overnight leader Pádraig Harrington shot a 69 to maintain his lead after the second round of the World Golf Championships-Bridgestone Invitational in Ohio, but his compatriots failed to strike back from disappointing first rounds.

Three-time major winner Harrington produced his best round of the year with a 64 yesterday to one from Tim Clark of South Africa and two from American Scott Verplank.

The Irishman picked up where he left off as he began his second round well, moving to seven under par after five holes.

He bogeyed the par-four eighth, the only blemish on his round, but rebounded at the 13th courtesy of a birdie from 30 feet.

"Shooting that score yesterday gave me a great chance for the tournament," Harrington said.

"Anything under 70 from here on in is going forward so I'm quite pleased to have shot 69."

The Dubliner admitted his second round had been less aggressive than his first but added: "I normally play the first rounds cautiously.

"I was a bit cautious today. I was more worried about my misses rather than having that sort of confident attitude and going after a few more pins.

"You know that if you shortside yourself you're going to have difficulty getting up and down. But you've got to make some birdies.

"My short game has been good enough, so I probably should be a little bit more aggressive over the weekend."

Verplank matched playing partner Harrington with a 69 that left him five under while Prayad Marksaeng briefly moved alongside the Dubliner but three bogeys on the way in, having started on the 10th, meant he had to settle for a 70 to stay four under.

Clark, also among the late starters, sank three birdies on the back nine to make the turn at seven under but a bogey at the third forced him to sign for a 68.

Spain's Alvaro Quiros made a big move into contention with a 65 to move from two over to three under.

Darren Clarke, 2003 champion, is next best of the Irish after a 70 left him one over, three ahead of Graeme McDowell who improved on yesterday’s 73 with a 71.

Rory McIlroy improved by five shots but a level par 70 left him on five over, while Shane Lowry added another 78 to move back to 16 over, with only Japan’s Yuji Igarashi between him and the foot of the leaderboard.

World number one Tiger Woods, a six-time winner at Firestone, was another early starter and recorded a 70 to stay two under, while playing partner Sergio Garcia carded a 72 to fall back to level par.

Four birdies in his first 12 holes moved England's Oliver Wilson to five under par for the week but three bogeys on his back nine left the Ryder Cup player with a 69, two under for the week.

Open champion Stewart Cink finished at two under par alongside Woods and Wilson but Ian Poulter is one over after slumping to a 74.

Compatriots Nick Dougherty and Lee Westwood both shot 71 to return to level par.