Denmark have named 21 players of the 26-man squad and will reveal the final five following the last round of European fixtures.
They take on Tunisia on 22 November.
The final squad must be delivered to Fifa by 13 November, before the tournament starts on 20 November.
“Many things can happen,” said Denmark manager Kasper Hjulmand. “It’s unsolvable, but it’s the right way to do it – there are two games left for many of our players, and that can easily change things.”
Denmark preliminary squad
Goalkeepers: Kasper Schmeichel (Nice), Oliver Christensen (Hertha Berlin).
Defenders: Simon Kjaer (AC Milan), Joachim Andersen (Crystal Palace), Joakim Maehle (Atalanta), Andreas Christensen (Barcelona), Rasmus Kristensen (Leeds United), Jens Stryger Larsen (Trabzonspor), Victor Nelsson (Galatasaray), Daniel Wass (Brondby).
Midfielders: Thomas Delaney (Sevilla), Mathias Jensen (Brentford), Christian Eriksen (Manchester United), Pierre-Emile Hojbjerg (Tottenham).
Forwards: Andreas Skov Olsen (Club Bruges), Jesper Lindstrom (Eintracht Frankfurt), Andreas Cornelius (Copenhagen), Martin Braithwaite (Espanyol), Kasper Dolberg (Sevilla), Mikkel Damsgaard (Brentford), Jonas Wind (VfL Wolfsburg).
— Ferdinand A Baah