It was revealed yesterday that United had agreed terms with Spurs over a fee for the midfielder.
Bilic said: “Don’t worry — Luka won’t be affected by talk of his future. No way.
“We talk a lot and Luka always puts his team-mates ahead of his own ambitions. He’s very responsible, he knows he has to have a great tournament and be on top of his game for us to do what we are aiming to do.
“Talk of his future will only motivate him and boost his confidence. It’s also my job to turn that to his advantage, to make sure that extra bit of pressure will drive him and will not be a weight on his shoulders.
“As Croatia manager and a fan, or his older brother, his father or his friend, I want him to be happy. When I called him and said he was already with a big club at Tottenham I only wanted to tell him that he shouldn’t panic and say to himself: ‘I have to leave’.
“But now it’s going to be his and the club’s decision. He knows what I think and it’s a conversation that will stay between me and him.”