Ex-MLB slugger and steroid snitch Jose Canseco says he can prove former Yankees star Alex Rodriguez is cheating on new fiancée Jennifer Lopez with Canseco's ex-wife, Jessica Canseco.

Canseco, 54, in a tweet Wednesday challenged Rodriguez to take a polygraph test to prove that he’s not lying when it comes to the allegations. He also said tweets from his ex-wife forced him to defend himself.

JOSE CANSECO'S EX-WIFE CLARIFIES ALEX RODRIGUEZ CHEATING CLAIM AMID ENGAGEMENT TO JENNIFER LOPEZ

“Jessica you're calling me a liar you just forced me to defend myself and tell the truth here comes the biggest story ever about Alex Rodriguez and yourself the truth hurts do not turn away or hide from a polygraph,” he tweeted.

Canseco also apologized to Lopez for getting her “caught up in the middle of this,” but he said the “truth has to be told.”

Jessica Canseco, in a pair of tweets Tuesday, shot down the rumors that she was seeing Rodriguez.

“Those false accusations Jose is making are not true! I have known Alex for many years and haven’t even seen him for over 5. I certainly did not sleep with him. I am friendly with both him and Jennifer. As for Jose he can keep playing with his Alien friends,” Jessica Canseco wrote.

She added: “In fact I don’t even get on twitter had to download app again and don’t watch tv and had no idea any of this was going on. Last time I saw Alex he was with Torrie [Wilson] and I brought my boyfriend over for dinner. We are just friends my god.”

Jose and Jessica were married from 1996 to 1999. Jose Canseco said Sunday he was there when Rodriguez called her.

Canseco famously mentioned Rodriguez in his book “Vindicated” – a sequel to his jaw-dropping, tell-all book "Juiced" – claiming he introduced Rodriguez to a steroids distributor and that Rodriguez slept with Jessica at the time.

Rodriguez hasn’t responded to the rumors.

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Jose Canseco’s remarks came a day after Rodriguez and Lopez announced their engagement. The pair celebrated their two-year dating anniversary on Feb. 4.