The Belgian impressed in the Bundesliga last season during a season-long loan at Werder Bremen, and amid talk the Blues could be set to loan him out again this winter, Leverkusen are one club keen on signing him.
"We made no secret of our interest in Kevin De Bruyne right from last summer," Voller told Germany's Sky Sport. "There are many clubs interested in him.
"Regardless of our league position, we're always looking for new players.
"It's possible that we do sign somebody this winter, but then again, we could go into the second half of the season with the same team and look to do something next summer.
"If you do anything, then it's got to be a top alternative to what we've already got here."
Leverkusen slipped up for the first time at home on Sunday, falling seven points adrift of league leaders Bayern Munich with a game to go before the midway stage of the season.
De Bruyne has made eight appearances this season, with four of them as a starter.