Padraig Harrington set for Olympics after Graeme McDowell joins Rory McIlroy in pulling out

"It would be a huge honour for me to represent Ireland at the Olympic Games, having played an active role in golf's bid to be re-included in the Olympic Games programme," said Harrington, a three times major champion, in a statement.

World number four McIlroy announced his withdrawal on Wednesday because of fears over the Zika virus which can cause birth defects.

Former US Open champion McDowell then issued a statement ruling himself out as replacement for the Northern Irishman because his wife is due to give birth a couple of weeks after the Games.

"As many within golf will know, my wife Kristin is pregnant and is due to have our second child just a couple of weeks after the Olympic Golf competition concludes," said McDowell.

"I made the decision many months ago, before I was on the team, that I would not play or travel outside the U.S., where I and my family live, in the weeks running up to the birth," he added.

The decision left Harrington as next in line, based on current ranking points.

"I will work very hard over the next few weeks to achieve this selection," he said in a statement issued by the Olympic Council of Ireland.

The Irish golf team will be announced next month, with Shane Lowry sure to be one of the players.

The International Golf Federation said it was disappointed but recognised the "unique circumstances" McDowell faced.

The two Northern Irishmen join a growing list of players deciding not to go to Brazil.

Fiji's Vijay Singh, Australia's Marc Leishman and South Africa's former Masters champion Charl Schwartzel have all pulled out of the Olympics due to concerns over Zika.

Australian world number eight Adam Scott and South Africa's world number 14 Louis Oosthuizen have also opted out for scheduling reasons.

US health officials have concluded that Zika infections in pregnant women can cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies.

The World Health Organization has said there is strong scientific consensus that Zika can also cause Guillain-Barre, a rare neurological syndrome that causes temporary paralysis in adults.

Medical experts had a mixed response to McIlroy's decision. Derek Gatherer, a virus expert at Britain's Lancaster University, said if the golfer was "contemplating becoming a father within a year or so, then it was a perfectly reasonable precaution to stay away from regions of active Zika transmission".

But Jonathan Ball, a professor of molecular virology at the University of Nottingham, said: "Obviously I don't know the reasons for this decision, but it does strike me as being extreme.

"The chances of being infected by the Zika virus is low, especially if you protect yourself from mosquito bites by covering up and using a good insect repellent."