Fulton County Superior Court Judge Robert McBurney ordered that Graham will be required to testify on Aug. 2. The judge's certification filed on Monday described Graham as a "necessary and material witness" to the grand jury probe. The development was reported earlier by WSB-TV.

Graham's office did not immediately respond to a request for comment. The senator's attorneys said last week he would not comply with a subpoena issued by the grand jury. The grand jury also subpoenaed members of Trump's former legal team, including personal lawyer Rudy Giuliani.

Fulton County District Attorney Fani Willis had requested the special jury in January in part due to its subpoena power, which she argued was needed to compel witness testimony.

The probe was launched after Trump was recorded in a Jan. 2, 2021, phone call pressuring Georgia's secretary of state to overturn the state's election results based on unfounded claims of voter fraud.

During the phone call, Trump urged Secretary of State Brad Raffensperger, a fellow Republican, to "find" enough votes to overturn his Georgia loss to Democrat Joe Biden.

The transcript of the call quotes Trump telling Raffensperger: "I just want to find 11,780 votes," which is the number Trump needed to win Georgia.

Trump has denied wrongdoing in the phone call.

Legal experts have said Trump's phone calls may have violated at least three state election laws: conspiracy to commit election fraud, criminal solicitation to commit election fraud and intentional interference with performance of election duties.