World number two Dustin Johnson, who won his first major title at the US Open Golf Championship in June, won't play in the Rio Olympics because of concerns over the Zika virus.

In a statement released to the Golf Channel on Friday by his agent, David Winkle of Hambric Sports Management, Johnson said his hopes of expanding his family with fiancee Paulina Gretzky meant it would be "irresponsible" to risk contracting the mosquito-borne virus that has been linked to birth defects.

"As an athlete, I can think of no greater honor than representing the United States in the Olympic Games," Johnson's statement said. "However, after much careful consideration and discussion with both my family and my team, I have made the decision to withdraw from the 2016 Olympic Games.

"This was not an easy decision for me, but my concerns about the Zika Virus cannot be ignored," added Johnson, who has a one-year-old son, Tatum, with Gretzky.

"Paulina and I plan to have more children in the near future, and I feel it would be irresponsible to put myself, her or our family at risk. I believe I am making the right decision for me and most importantly, my family."

Johnson joined an exodus of top golfers from the Games which has taken the sheen off the sport's return to the Olympics after a 112-year absence.

World number one Jason Day, Northern Ireland's Rory McIlroy, Australian Adam Scott and Japan's 17th-ranked Hideki Matsuyama have all mentioned Zika as a consideration in opting out of Rio.

Johnson, who indicated last week that he expected to play in Rio, is the first eligible US golfer to pull out, but he might not be the last.

Former world number one Jordan Spieth has also voiced interest in playing but has yet to confirm that he will.