Former Secretary of State George Shultz told CBS News’ John Dickerson on CBS News’ “Face the Nation” that President Donald Trump should admit that his claim that he was wiretapped by President Obama was a “mistake.”

“He’s got to figure out a way to get out of it,” said Shultz, who served in the cabinets of Republican Presidents Richard Nixon, Gerald Ford, and Ronald Reagan. “To say, ‘Okay, I made a mistake,’ and go on from there. Because you’ve got to establish an atmosphere of trust. Trust is the coin of the realm. And you need to do that with other leaders or people you’re going to deal with, including your adversaries.”

Mr. Trump has provided no evidence for the claim, which has been roundly rejected by Republicans and Democrats alike.

Shultz said he learned the lesson about trust as a Marine in World War II when he was taught that he should only aim a gun at someone if he was willing to pull the trigger. “If I can’t trust you, I can’t deal,” Shultz said. “But if I trust you, then I can deal. So trust is the coin of the realm, very important point.”

The former chief diplomat, whose tenure in the 1980s saw the Cold War come to a close, also said it was necessary for America to retain its leadership position in the world and stand close to its allies. “They need to hear that we’re in the alliance, full bore,” Shultz said. “And they’ve been hearing that, I think.”

Shultz also shared the advice he gave Rex Tillerson, Mr. Trump’s secretary of State. “I think the secretary of State has to establish two things,” Shultz said. “One, that he’s close to the president, and that he speaks for the president. And being close, the president listens to him. So together, they formulate the policy.”