(CNN) Longtime attorney for President Donald Trump Jay Goldberg says he's concerned Michael Cohen will lie to prosecutors to get leniency on his own charges.

"And I didn't accept the notion of 'flip,' " Goldberg told CNN's Erin Burnett. " 'Flip' means to me that when faced with the potential of spending time in jail, he will tell the truth. I don't think that was what the President was concerned about and that's not what I'm concerned about."

He added that Cohen may say what he needs to get "leniency" -- and "that doesn't necessarily mean he tells the truth."

Goldberg also expressed his concern about special counsel Robert Mueller's deputy, Andrew Weissmann. He said Weissmann is of "questionable honor" and that it was naive to believe he would not be involved in the investigation.

"After all, Mueller is not sitting and working on the case himself," Goldberg said. "It's the chief deputy that calls the shots."

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