The striker remains at Parkhead despite four bids from Norwich City during the January transfer window.
The Celtic manager told the Daily Record: "I will need to speak to Peter Lawwell about it but the contract is still there.
"My advice to Gary would be to sign it. Whether he wanted to go now or in the summer. If the money is there in front of you from Celtic then take it.
"We had a chat with Gary in Marbella and he said, 'Look, I want to stay'. We will look at his position in the summer. I don't want to stop his progression, but we feel he has still got a lot to offer here before he moves on."
The 24-year-old still has 18 months on his current contract.
Hooper has 23 goals in 33 games for the club this season.