FILE PHOTO: A view shows a house of parents of Sayfullo Saipov, the suspect in the New York City truck attack, on the outskirts of Tashkent, Uzbekistan November 2, 2017. REUTERS/Mukhammadsharif Mamatkulov/File Photo

NEW YORK (Reuters) - A federal judge on Monday ordered prosecutors to petition the U.S. State Department to let relatives of Sayfullo Saipov, the Uzbek national charged with killing eight people on a New York City bike path, into the country to testify at his trial.

U.S. District Judge Vernon Broderick said in a written order that Saipov’s parents and two sisters would be “important mitigation witnesses” in the second phase of Saipov’s trial, when a jury will decide whether he should be sentenced to death.

Saipov’s lawyers said in a motion in May that the State Department had refused to grant Saipov’s relatives permission to enter the United States without visas, and asked the Manhattan judge either to reverse that determination or order the prosecutors to intervene.

Broderick said in Monday’s order that he did not have the authority to overrule the State Department, but said he could order the prosecutors to file a petition. He noted that the State Department could still deny that petition, and said prosecutors and Saipov’s lawyers should explore “alternative arrangements” to get testimony from Saipov’s relatives if they cannot appear in person.

A spokesman for the office of U.S. Attorney Geoffrey Berman, which is prosecuting the case, declined to comment. A lawyer for Saipov could not immediately be reached.

Saipov, 31, is scheduled to go to trial on April 13.

He was arrested on Oct. 31, 2017 after driving a truck down a bike path in lower Manhattan, killing eight people. Islamic State claimed responsibility for the attack, the deadliest assault in New York City since Sept. 11, 2001.

Saipov has pleaded not guilty to charges, including eight counts of murder, 18 counts of attempted murder and providing material support to Islamic State.