A federal judge expressed “concern” that the U.S. scared off American International Group Inc. from joining a lawsuit by Maurice “Hank” Greenberg, its former chairman, challenging the insurer’s 2008 federal bailout.

“I had this lingering concern,” Judge Thomas Wheeler said at a hearing in the U.S. Court of Federal Claims in Washington on whether to dismiss Greenberg’s lawsuit.

“I don’t want to call them threats necessarily. Would I be intimidated by all of this?” Wheeler asked lawyers for the U.S., AIG and Greenberg’s Starr International Co.

Starr, Greenberg’s closely held investment firm, sued the government for $25 billion in 2011, calling the assumption of 80 percent of AIG stock by the Federal Reserve Bank of New York in September 2008 a violation of the constitutional rights of shareholders to due process and equal protection of the law.

Starr also claims AIG’s board, which Greenberg said was unduly influenced by the government, failed to conduct a full and independent review of whether to join the lawsuit. Starr asked Wheeler to find the board wrongfully decided to stay out of the case.