Watson was greeted by a standing ovation at the last hole Photos from Olympia Fields

The 53-year-old, who won the title in 1982, sank an eight-foot par putt at the last hole to join Brett Quigley at the top of the leaderboard after the first round.

"Who would have thought it?" an overwhelmed Watson said afterwards.

"I had tears in my eyes. A lot of emotion there."

Watson, who now plays on the senior tour and was only appearing in the US Open because of a special invite from the USGA, was cheered on by a raucous crowd at Olympia Fields.

Watson revealed that he was using a similar putter to the one he used in his prime - when also he won five Open Championships.

LEADERBOARD (US unless stated) -5 T Watson, B Quigley -4 J Leonard, JD Blake -3 J Furyk, S Leaney (Aus) -2 T Gillis, M Calcavecchia, I Leggatt (Can) Latest scores

"I listened to my caddy. He said put that old putter in your bag and that's what I did. I put it in, and the magic started," said Watson.

Watson's caddy, Bruce Edwards, who has the incurable Lou Gehrig's disease, said he too had been overwhelmed by the crowd's response to Watson's efforts.

"I don't know when I won't be able to do it any more," Edwards said. "I'm a proud man right now."

Despite his brilliance on Thursday, Watson admitted he did not know if he could keep it up for three more rounds.

"When you get to our age you've got a lot of worn out parts. My back wasn't feeling too well today. The body was a little stiff," said Watson.

"We'll just have to see. I'm hitting the ball well enough. It's just a matter of being able to deal with the pressure.

Tiger Woods did not enjoy his best day Day one round-up

"Whether I can do that or not I don't know, but I'm going to give it enough, don't worry about that."

Quigley, the 33-year-old qualifier who had missed the cut in his previous two US Open appearances, said a change in attitude was behind his turnaround in form.

"I am an underachiever - I think I am finally realising (that) and taking steps to get through it," he said.

"I never felt nervous today and just played well. I felt good with the putter and managed to keep the momentum going."

Tiger Woods refused to be disappointed despite an unconvincing start to the defence of his US Open title.

Woods, who opened with a level-par 70, lies five shots behind the leaders.

"In a major championship, you have to be that way," Woods said. "You have to keep plugging along.

"You've got be smart in US Opens and, when I trusted my swing, I hit it perfect today. I've just got to do that more often.

"I feel very good how I managed my game - I got it around and I kept myself in the tournament."

The greens are really difficult to putt here, especially if you get past the hole Ernie Els

Playing partner and Open champion Ernie Els was satisfied with a one-under-par 69 that included just one birdie.

"The greens are really difficult to putt here, especially if you get past the hole," said Els.

"But I'm happy with the way I played, I just didn't get much out of it."