"Alex Hales has made himself unavailable for selection for personal reasons and no timetable has been set for his return to action," Nottinghamshire said in a statement on their website.
Hales missed Nottinghamshire's 50-over match against Lancashire on Friday.
It is unclear whether the 30-year-old opening batsman, who has played 70 ODIs, will be available for England's one-dayer against Ireland on May 3 or a five-match ODI series and Twenty20 international against Pakistan.
Those matches will be England's final internationals before they begin their campaign to win their maiden 50-over World Cup during the May 30-July 14 tournament on home soil.
(Reporting by Sudipto Ganguly in Mumbai; editing by Peter Rutherford)
