Houllier has been told that Larsson is remaining at Birmingham for the rest of the campaign until his contract expires in June. But he could revisit the possibility of signing the former Arsenal player when he becomes a free agent.
He said: "I knew Larsson's contract was up at the end of June, so obviously I was interested because he's a good footballer, good passer. He can play different positions. I think he even played right-back at Arsenal.
"I think he would have been good for us. He's staying at Birmingham for now. But in June the door will still be open. I thought it (any deal) would happen in June anyway. Remember, Birmingham have qualified for the Carling Cup final.''
Houllier confirmed midfielder Stephen Ireland will not be leaving the club during the current transfer window. Ireland is currently sidelined with a knee injury but has struggled to make an impression under Houllier.
Houllier said: "Will Ireland still be here in February? Oh, yes. Do I see him going anywhere? No. He should be back next week (from his injury).''
Warnock has been linked with a loan move back to his former club, Liverpool.
Houllier said: "He trained well this morning. He is competing to get his place back.
"Ciaran Clark has done well and so has Nathan Baker but, yes, there are two or three days left before the end of the transfer window. Anything can happen.''