World number 15 Patrick Reed has pulled out of the PGA Championship and next week's Irish Open.
The 24-year-old United States player was due to compete at Wentworth from Thursday before moving on to the event at Royal County Down, Newcastle.
He has opted to play in this week's Crowne Plaza Invitational in Texas.
"We will not be able to travel overseas at this time. My sincere apologies go to the organisers of both events, and to the fans," said Reed.
The Irish Open takes place from 28-31 May and is being hosted by world number one Rory McIlroy's charity foundation.
A statement issued by Reed said: "I am really looking forward to playing on the European Tour this year which makes me even more disappointed to withdraw from Wentworth and the Irish Open.
McIlroy, 26, is back at Wentworth to defend the title he won 12 months ago.
US Open champion Martin Kaymer is also in the field but has called on the European Tour to move its flagship event to later in the season.
"The only thing this tournament suffers with is the greens every year," he said.
"Talking to a few members they said if you come here in six weeks the greens are perfect. For us players it would be even more fun to play the course then."
Four-time major winner McIlroy has been instrumental in assembling a high quality field for the Irish Open.
Among those playing at the famous links course at the foot of the Mourne Mountains are Kaymer, Ernie Els, Sergio Garcia, Rickie Fowler, Luke Donald and Lee Westwood.
McIlroy's fellow major winners from Northern Ireland, Graeme McDowell and Darren Clarke, are also taking part.