Ireland outhalf Johnny Sexton is champing at the bit to get into action against Romania in his side's Rugby World Cup opener on Saturday after a six-month spell on the sidelines due to injury and a three-match suspension.

Sexton needs 34 points to eclipse Ronan O'Gara's total of 1 083 as Ireland's top scorer, and though he is now 38-years-old and not necessarily needed against a team that Ireland has beaten in all nine previous meetings, Sexton is set to start and captain Andy Farrell's side.

"I'm delighted to be back," Sexton said on the eve of Ireland's opening game. "Playing for Ireland is always special, extra special when it comes to World Cups, so I'm very, very happy to be back in the team."

Sexton has recovered from a groin injury sustained in Ireland's Grand Slam victory over England in March, and he has also served a ban for "confrontational and aggressive" behaviour towards match officials following May's Champions Cup final.

"Getting back fit from the injury was the first challenge, and then once I got back from that, then being able to reintegrate with the team and getting back to speed," Sexton added.

"When you're a little bit behind at the start, you've got to work harder to stay fit and improve your fitness, so that's what I've tried to do over the last couple of months."

Set to retire after the World Cup, the tournament represents Sexton's last chance to break O'Gara's record, and he shrugged off suggestions that age and injury might limit his chances.

"I'm very happy with where I'm at, obviously going into the game a little bit different but hopefully I can lean back on experiences from before ... I don't think I've lost any range, but we won't find out until the big days," he said.