WASHINGTON — Authorities in Tunisia have agreed to allow FBI investigators access to a detained militant suspected of playing a role in the Sept. 11 attacks on US diplomatic facilities in Benghazi, Libya, US officials said Friday. Under an arrangement worked out between Tunisian and US officials, American investigators will be allowed to interview Ali Ani Al-Harzi under the supervision of Tunisian officials. The arrangement was first made public in a written statement issued Friday by two Republican US senators, Saxby Chambliss, vice chairman of the Senate Intelligence Committee, and Lindsey Graham, a senior member of the Senate Armed Services Committee. The senators said that while it was “unfortunate” that it had taken some time for the agreement to be reached, “allowing American investigators in person access will make the interview more meaningful and is a welcome breakthrough in our efforts to find the perpetrators to the Benghazi ... attacks.” Earlier this week, Graham wrote to the Tunisian government advising them how important it was to him and other US legislators for Al-Harzi to be made available to US investigators. Meanwhile, Chambliss urged the FBI to seek access to Al-Harzi and any other individuals who might be detained in connection with the attacks. A US government source said it was possible that the senators' pressure may have helped convince the Tunisians to allow FBI investigators to interview Al-Harzi, who was initially arrested in Turkey in October but later sent back by Turkish authorities to his native Tunisia. US sources have said that Al-Harzi is suspected of participating in the Benghazi attacks in which Christopher Stevens, the US Ambassador to Libya, and three other US officials were killed. His precise role in the attacks was unclear, the officials said, and there was no proof he was a leader in the attacks. The Daily Beast news website reported on Oct. 23 that shortly after the Benghazi attacks began, Al-Harzi posted an update about the fighting on an unspecified social media site. The Daily Beast said this was one of the first clues for US intelligence agencies seeking to find out who was behind the violence. — Reuters