The Dutch football association said the squad announcement has been moved back two days to Wednesday, May 27th.
Players like leading scorer Memphis Depay, Bournemouth’s Justin Kluivert and Arsenal defender Jurrien Timber are among those doubtful for next month’s tournament in Canada, Mexico and the United States.
"By taking two extra days, we can be more certain that the players we are going to select are in good shape," Koeman said in a statement released by the football association.
"Moreover, it gives us the opportunity to personally see, speak to and assess several players who are in contention for the final selection during training days on May 25th, 26th and 27th.
“This has no further impact on our original schedule, as preparation with the complete group starts on Saturday, May 30th. I would therefore like to utilise the extra time this offers to take all aspects into account in the choices we make regarding the final selection,” he added.
The Dutch fly to the United States on June 4th, and in the run-up to their first World Cup match against Japan on June 14th in Dallas.
They will play friendly matches against fellow finalists Algeria on June 3rd in Rotterdam and Uzbekistan on June 8th in New York.