WASHINGTON (AP) -- The government is trying to block questioning of Federal Reserve Chairman Ben Bernanke in a lawsuit by the former head of American International Group Inc.

The Justice Department told a federal appeals court Friday that high-ranking officials should not have to testify except in extraordinary circumstances.

Former AIG CEO Hank Greenberg sued the government over the $182 billion bailout of the insurance giant that has since been repaid. Greenberg claims the bailout terms were too onerous and is seeking at least $25 billion.

It is rare for a Fed chairman to be questioned in a lawsuit, but U.S. Court of Federal Claims Judge Thomas Wheeler ruled that Bernanke has firsthand knowledge of the bailout and should undergo questioning. Justice wants the appeals court to order Wheeler to block the questioning.