The Tynecastle manager is keen to retain the services of the Lithuanian defender, who led the club to their William Hill Scottish Cup triumph last season. But cash constraints mean they are unable to offer their top earner the same terms he currently enjoys.
Locke told the Edinburgh Evening News: "His contract is up at the end of the season, as everybody knows. It would be fantastic to keep him here, but I'm not sure what Marius' plans are. If I was a betting man, I'd probably suggest he will be on the move. You never know. He's a player I'd love to keep here."
He added: "I've spoken to him about his plans, but he hasn't made a decision at the moment. I'll give Marius all the time he needs.
"His contract is up in the summer and he still has a bit of time to decide what he wants to do. If he goes, good luck to him and we wish him all the best. He's been fantastic for the club. If he stays, we'll be delighted."
Zaliukas has not featured for the Gorgie outfit since he was ruled out for the season after injuring his ankle in Hearts 3-1 defeat to Dundee United at Tannadice on February 9.