The 32-year-old centre-back missed the Premier League run-in for Arsenal after suffering a leg injury in March. He was last night named in Domenech's initial party, but the coach has offered no assurances he will remain in the final 23-man group unless he is fully fit.
"William is one of the uncertainties, who are in the extended list but there is no guarantee of playing," Domenech told rmc.fr. "If he is fully operational he will be involved. If he is not he will be sent home."
Striker Karim Benzema, 22, was omitted from the preliminary squad after a below-par first season with Real Madrid. Domenech said: "He had a difficult year and I make my choices not always on the most visible criteria.
"(But) he is at an age that allows him to still fight to return as soon as possible to the France squad. It's a difficult moment for me, too. He has made efforts but there is a time to make choices. It's complicated. I know what it is like for the players, but I'm not sure the players imagine how hard it is for the coach."
Gallas was one of four Arsenal players included last night - along with Bacary Sagna, Gael Clichy and Abou Diaby - but team-mate Samir Nasri missed out along with former Gunner Patrick Vieira. Sagna told lequipe.fr: "It's great to see so many Arsenal players in the squad but the news of Nasri has put things in perspective.
"At these moments there is nothing one can say. I have not called him yet but no words can soothe him. He misses a World Cup. They (Nasri, Vieira and Benzema) must be surprised and disappointed. They are among the players who are regularly called up."