By Jonathan Stempel

(Reuters) - A federal judge said Bill Cosby's homeowner's insurance company must defend him against three civil defamation lawsuits in Massachusetts brought by several women who accused the once-beloved entertainer of sexual abuse.

In a decision on Tuesday, U.S. District Judge Mark Mastroianni in Springfield, Massachusetts left open the question of whether American International Group Inc must indemnify Cosby for damages he may be required to pay the women.

But the judge said Cosby's alleged sexual misconduct was "too far removed" from his alleged defamation to free AIG from coverage under a policy it issued in California, while the sexual misconduct exclusions in a Massachusetts policy were "ambiguous" at a minimum.

"The court cannot say ... that it was the intent of the parties to exclude the kinds of claims brought in the defamation cases," Mastroianni wrote. "If Cosby's interpretation is reasonable, and thus the language is at least ambiguous under these circumstances, he prevails."

Mastroianni said the indemnification question "must await the completion of trial or settlement."

AIG had no immediate comment on Wednesday, and lawyers for the New York-based insurer did not immediately respond to requests for comment.

Lawyers for Cosby did not immediately respond to similar requests. They have said AIG was required to cover Cosby's defense costs against the women's claims, even if those claims were groundless.

Homeowner policies typically cover personal injuries, such as when a person falls down on an insured's property, while "excess" policies such as Cosby's carry enhanced protections.

AIG had sought declarations that Cosby's policies excused it from defending and indemnifying him against personal injury claims "arising out of" sexual misconduct, as distinct from personal injury claims such as defamation.

The women had alleged that Cosby harmed their reputations, including through his representatives, by calling them liars after they publicized their allegations.

Last November, a federal judge in Los Angeles said AIG must defend Cosby against claims in a similar case by the actress and model Janice Dickinson because the sexual misconduct exclusions did not unambiguously bar coverage.

Cosby, 79, must still defend himself in a Pennsylvania criminal case where he was charged with having in 2004 sexually assaulted a former basketball coach from his alma mater, Temple University. He has pleaded not guilty.

More than 50 women have accused Cosby of having subjected them to unwanted sexual abuse in incidents dating to the 1960s.

The case is AIG Property Casualty Co v. Green et al, U.S. District Court, District of Massachusetts, No. 15-30111.

(Reporting by Jonathan Stempel in Washington, D.C.; Editing by Tom Brown)