The manager reiterated his interest in bolstering his squad, but notes it could be hard to persuade players to make the switch halfway through a season.
The reigning champions have experienced an indifferent season approaching the halfway point, as five losses in the Premier League have left them in seventh position, eight points off table-topper Liverpool.
Moyes, however, has seen his side improve in recent matches following four straight wins in all competitions, with United topping its Champions League group and reaching the semifinals of the Capital One Cup.
United's patchy league form had led to rumors the Scot could bolster his ranks, especially in midfield, but Moyes feels his targets are unlikely to leave their clubs midway through the campaign.
"We will look [at targets]," Moyes said. "But I wouldn't turn around and say that I'm massively sure that we will get them. Because a lot of the players we would be interested in wouldn't be available for us in that month of January. But we'll certainly be looking."
United struggled to sign players in the summer window too and only sealed Marouane Fellaini on deadline day, with bids for Cesc Fabregas and Ander Herrera falling flat.