The Danish centre-back has yet to put pen-to-paper on a new deal at Anfield.
"We are going to sign a new defender in January, there's is no doubt about that," Galliani told Denmark's tipsbladet.dk.
"We have a list of three or four names that could be used in the defence. Agger is one of those names.
"We will for sure make a bid for one of them in January."