Ryan O'Neal has filed a defamation case against an assistant of his late partner Farrah Fawcett, amid claims he appropriated an Andy Warhol work.
O'Neal alleges Craig Nevius made false statements to the media that prompted the University of Texas to demand the 1979 Warhol portrait of Fawcett.
In a complaint filed in Los Angeles, O'Neal accuses Nevius of making "false, malicious and defamatory accusations".
Nevius responded by claiming the actor hoped to "harass [him] into silence".
In a legal action launched last week, the University of Texas claimed Fawcett had bequeathed the work - one of two Warhol made of the Charlie's Angels star in 1979 - to its Austin campus.
Actor O'Neal, 70, claims the silkscreen belongs to him, not Fawcett.
O'Neal's spokesman said the painting had been a gift to O'Neal from Warhol and that he expected to be "completely vindicated in the courts".
In his legal action, O'Neal alleges that the university is acting based on false statements that Nevius made to the media.
The actor is claiming damages in excess of $1 million (£621,450) for defamation, intentional infliction of emotional distress and negligent infliction of emotional distress.
Farrah Fawcett - who attended the University of Texas in the 1960s - died of cancer in 2009 at the age of 62.
Nevius, who worked with the actress on a documentary about her illness, has denied accusing O'Neal of stealing the portrait.