Jordan Spieth has confirmed "health concerns" amid fears over the Zika virus were behind his decision to pull out of the Olympic Games.

The American's withdrawal was confirmed on Monday by International Golf Federation president Peter Dawson, who claimed there had been an "overreaction to the Zika situation".

But Spieth, speaking at Royal Troon on Tuesday ahead of The Open, felt his call was justified.

"Health concerns were my reasons," said the two-time major winner. 

"This was probably the hardest decision I've ever had to make in my life. This was harder than trying to decide what university to go to, whether to turn professional, to leave school.

"I've bounced back and forth with it. Ultimately a decision had to be made yesterday [Monday], so I made it."

Spieth's decision means none of the world's top four male players will compete in Brazil, with Jason Day, Dustin Johnson and Rory McIlroy having already pulled out.

The mosquito-borne Zika virus has been linked with birth defects and competitors in some other sports have also opted against taking part in Rio because of it.

Spieth insisted he values golf's return to the Olympic arena for the first time since 1904 and claimed he will prioritise featuring at the Tokyo Games in 2020.

"I'm a huge believer in Olympic golf, a huge believer in paying for your country. I looked forward to the summer and winter Olympics. It's the most exciting sporting event for me to watch on TV.

"This year I had to try to weigh risk that doesn't present itself every year. At the time I had to make decision, I felt this was the right move for me.

"Nobody is going to understand what it's like in my shoes.

"I believe I'm making the right decision for myself, for my future and for those around me.

"I'll make it a goal to be at Tokyo in 2020. I'll make it a significant goal."