Former Secretary of State John Kerry John Forbes KerryThe Memo: Warning signs flash for Trump on debates Divided country, divided church TV ads favored Biden 2-1 in past month MORE said Sunday that President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE saying he'll negotiate a better climate deal compares to O.J. Simpson searching for "the real killer."

"When Donald Trump says to the world, well we're going to negotiate a better deal ... he's going to go out to find a better deal?" Kerry said on NBC's "Meet The Press."

"That's like O.J. Simpson saying he's going to go out and find the real killer. Everybody knows he isn't going to do that because he doesn't believe in it, because if he did believe in it, you wouldn't pull out of Paris," Kerry continued.

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Simpson, a former NFL player, was acquitted in 1995 after a lengthy public trial for the murders of his ex-wife and her friend. Simpson denied guilt, but public opinion was strongly against him even after his acquittal.

Kerry also referenced Trump's reported denial of climate change. He chided the administration for being unable to say whether or not the president "believes that climate change is a hoax."

He questioned what Trump knows that those across the world who urged the president not to pull out of the Paris climate agreement don't know.

If you truly understand the science, Kerry said, there is "no way that you cannot conclude that there's an urgency to doing something, and you would not pull out of Paris."

He added that the majority of Americans support action on climate change.

Trump last week announced his decision to pull the United States out of the Paris climate change agreement.

He cast his decision as one that puts the United States first, a central theme of his presidential campaign.