Sydney: Australian all-rounder Andrew Symonds admitted he should have been given out long before he made his unbeaten century against India at the Sydney Cricket Ground on Wednesday.

Symonds smashed 137 not out to help Australia reach stumps in a strong position at 376 for seven after they had slumped to 134-6 in the middle of the day.

Symonds unleashed his full power on the Indian bowlers, striking 17 boundaries and two sixes, but later admitted he was lucky because he had edged a catch behind off Ishant Sharma when he was on 30.

The Indians appealed confidently but West Indian umpire Steve Bucknor gave Symonds the benefit of the doubt.

"I was very lucky. I was out when I was 30, given not out," he told a news conference after the close of play.

"That's cricket though. I can sit here and tell you about my bad decisions as well, but I won't. That's the game. It's just one of those things."

Symonds had another let-off on 48 when the third umpire, Australian Bruce Oxenford, turned down a stumping appeal off Anil Kumble despite having the benefit of video replays.

The officials had already been in the spotlight after English umpire Mark Benson incorrectly gave the Australian captain Ricky Ponting out for 55, leg before wicket to Harbhajan Singh, but Symonds was quick to defend the umpires.

"You've got to keep the human element in there. It creates a different feel," he said.

"I don't think the game needs to go that every decision gets referred. There's ways to improve it, but let's not push and prod it too much.

"It's a great game. People make mistakes, players make mistakes every day, umpires make mistakes, too.

"It's how you handle them and how you keep going after those mistakes are made."

The 32-year-old Symonds hardly played another false shot after reaching his half-century, piling on 98 runs in the final session to get within sight of his highest Test score of 156.

"It's always a great feeling to score a hundred. It's a feeling of satisfaction," he said.