Former Defense Secretary Leon Panetta said Wednesday on "Your World" that President Trump is within his rights to negotiate and converse with Russian President Vladimir Putin.

Panetta, who served as President Bill Clinton's chief of staff and President Barack Obama's CIA Director and defense chief, said Trump should try to find common ground with the controversial leader.

"Putin has read a message of weakness in the United States for a long time and he takes advantage of weakness, that's his nature," Panetta said, responding to critics of Trump who say he is too cozy with the former KGB agent.

Panetta, who also served in Congress as a California Democrat, said "presidents talk to kings and emperors and tyrants regardless of whether or not they were elected with any kind of democratic process."

He told Cavuto that one of his main concerns is that Trump must be honest with a man like Putin.

"He is somebody you have to be very straight with, and if you try to cater to him, he will take advantage of it," Panetta said.

Panetta added that Trump should also be unafraid to tell Putin when "lines" are crossed - such as aggression against Ukraine or using a prohibited nerve agent to poison a diplomat on British soil.

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