Lambert has grounded his star striker after the forward suffered a groin problem during last weekend's victory over Norwich City.
He is insistent that if Benteke does not feature at all next week against Hull City that he won't be travelling with Belgium.
He said: "Christian is off his crutches which were used to take the weight off his injury. He's a lot happier within himself.
"It's not as bad as we first thought. The worst fear was that he was going to be out for a considerable time. The doctors are pretty happy with him.
"But if he doesn't play for us, then I'm not sure he will be fit for Belgium.
"He's got to go. The rules are that the Belgians have to see him themselves. I certainly wouldn't think he'll not be fit for us but play for them. We're his club."