Harrington made a strong start after a week's break

Padraig Harrington lies just one shot behind leader Tim Clark after a rain-hit opening round of the Tour Championship in Atlanta.

Harrington had a three-hour delay during his round but finished strongly with birdies at his last four holes for a seven-under-par 63.

Clark equalled the course record of 62 thanks to three birdies in his first four holes and an eagle at the 15th.

Tiger Woods is well in contention on four under after 11 holes.

Harrington was one of only 10 players in the 30-man field to complete their round.

He had completed 12 holes when an approaching storm stopped play but the break came at the right time for the Irishman, who regrouped superbly.

"The delay was probably good for me. I got a little bit frustrated through the front nine," said Harrington, who missed last week's BMW Championship, the third event in the US PGA Tour's new play-off series.

"I missed a couple of putts and this, that and the other and I thought it could be better.

"I made good birdies at 10 and 11 but still it just wasn't 100% and it was probably good for me to get off the course and regroup.

"I felt a lot sharper when I came back out. If I had played last week, I certainly wouldn't have shot the score I shot."