Spieth and many of the world's top golfers will compete this week at the World Golf Championships Bridgestone Invitational at Firestone Country Club in Akron, Ohio.

But with world number one Jason Day of Australia joining the list of top names backing out of golf's Olympic return over his concerns about the Zika virus, the hot topic ahead of today's opening round was Rio.

"Right now, I'm uncertain," Spieth said. "I have not received enough information to make an informed decision either way or not, so as we gather more information I will be able to make a decision one way or the other.

"When I feel confident, I will make a decision either side." The world rankings of July 11 will determine rosters so players have until then to decide about playing or not.

Spieth's US compatriot, third-ranked US Open winner Dustin Johnson, says he intends to play while fourth-ranked Rory McIlroy said he will not go to Brazil due to Zika, which has been linked to birth defects and severe illness.

Ireland's Shane Lowry, the defending Bridgestone champion, and Northern Ireland's Graeme McDowell have said no. So have Aussies Adam Scott and Marc Leishman, South Africans Branden Grace, Louis Oosthuizen and Charl Schwartzel and Fiji's Vijay Singh.

Sweden's fifth-ranked Henrik Stenson and sixth-ranked American Bubba Watson, a two-time Masters champion, have said they will play. Also uncommitted is seventh-ranked US star Rickie Fowler.

"I've had to adopt my two kids. We can't have kids. So that aspect is completely wiped away," Watson said. "If I was the other way and I was planning on having more kids, I would not go. But I'm not. I'm in a situation where that's not happening. So my decision was a lot easier.

"My wife missed out on playing in the Olympic Canadian basketball team, she was hurt. She couldn't go to the Olympics. And every day, I mean, she probably thinks about it. I get to go to the Olympics. No matter what I finish, I don't care if I finish dead last. At the end of the week or at the end of my career I get to say I played in the Olympics, and I'd be one up on Jack Nicklaus."

Latest News from Sports News Desk