The Manhattan district attorney’s decision to sue key congressional Republicans to prevent one of his own rogue prosecutors from testifying on Capitol Hill signals a sharp escalation in the battle between Alvin Bragg and federal lawmakers over the indictment of President Trump.

The filing asks a federal judge to block the subpoena issued by the House Judiciary Committee chairman, Jim Jordan, and other Republicans to Mark Pomerantz, who quit Mr. Bragg’s office in frustration for what he perceived as the district attorney’s reluctance to charge Mr. Trump. He subsequently wrote a book, “People v. Donald Trump,” to air his complaints against Mr. Bragg’s stewardship of the case.