The office of New York Attorney General Letitia James has asked a Manhattan trial court to issue an out-of-state subpoena to further its investigation of whether Capital One's $35 billion merger with Discover Financial Services violates the state's antitrust law.

In the Wednesday filing in state Supreme Court in Manhattan, James' office said its antitrust bureau is confidentially investigating the proposed transaction's effects on competition, under New York's Donnelly Act.