Fletcher was named United vice-captain at the start of the season, but has been unable to break into Van Gaal's first team and now looks set to move to the London side.
"Darren Fletcher is now in West Ham, I believe," Van Gaal told a press conference on Friday afternoon.
"So we have to wait and see."
Van Gaal also confirmed midfielder Michael Carrick was set for four weeks out with a muscle injury.
United posted this message on their website shortly after the press conference concluded: "Van Gaal has confirmed that Michael Carrick will be out for four weeks with a muscle rupture."
The website said Ashley young is getting "closer" to full fitness following his hamstring injury.
Source : PA