Ali ani al-Harzi, a Tunisian national with ties to the group's Africa terror cell, was temporarily detained by Turkish officials before being extradited to Tunisia shortly after the consulate raid in Benghazi. He is currently awaiting trial on terrorism charges in Tunis.
The assault by Libyan extremists ended with the death of U.S. Ambassador Chris Stevens and three other Americans.
The U.S. interrogations will be conducted under Tunisian supervision and be "consistent with their sovereignty and meets the needs of our investigative team," Sen. Lindsey Graham (R-S.C.) said in a joint statement with Sen. Saxby Chambliss (R-Ga.) issued Friday.
FBI investigators that have been leading the ongoing inquiry, which included a visit to the consulate site in Libya, will conduct the interrogations in Tunisia, according to a congressional source.
Both lawmakers heralded the agreement as a "welcome breakthrough" in the ongoing U.S. investigation of the consulate strike.
"We hope our interview of Ali Ani al-Harzi will bear fruit and we can bring to justice those responsible" for the consulate attack, they added on Friday.
At the time of his arrest, Al-Harzi was reportedly en route to Syria, likely to participate in the civil war between anti-government rebels looking to overthrow longtime President Bashar Assad, according to recent reports.
However, both Senate Republicans did express frustration over how long it took for Tunisia to allow American investigators to question al-Harzi.
“It is unfortunate it has taken this long to get an in-person interview as time is of the essence in cases like this," according to both lawmakers.
Graham has been at the forefront of the congressional effort to allow U.S. officials to question al-Harzi, personally pressuring Tunis to grant access to the terror suspect.
Tunisia's decision comes days after Graham sent a strongly-worded letter to Tunisan diplomats in Washington, threatening withdrawal of U.S. support for the newly-democratic regime if Tunis continued to keep al-Harzi under wraps.
"The Tunisian response to this situation is of the utmost importance and could have profound impacts on the relations between our two countries moving forward," Graham said in the letter sent Tuesday to Tunisia's Charge d’ Affaires to the United States Tarek Amri.
Whatever information al-Harzi provides U.S. officials could further flesh out the details of what happened that night in Benghazi, which Republicans claim remain murky at best.
On Thursday, U.S. intelligence officials provided new details on the attack, explaining that officers at the CIA annex in Benghazi went to the consulate to attempt a rescue after they were unable to receive help from local militias.
The U.S. officials said they provided the detailed account of the CIA’s role in the attack and rescue efforts to rebut media reports of delays in providing help to State Department officials.
The intelligence officials said there was no delay or order to “stand down,” and no interference or second-guessing from officials in Washington.
Recent reports also claim the diplomatic mission of the U.S. Consulate in Benghazi was a cover for a large-scale CIA intelligence operation inside Libya run out of the State Department facility.
The spartan outpost in Benghazi was one of several intelligence hubs set up by CIA in the aftermath of the Libyan revolution, which forced longtime leader Moammar Gadhafi from power.