WASHINGTON (CNN) -

The suspected ringleader of the deadly terror attack on the U.S. diplomatic compound in Benghazi, Libya, will remain jailed until trial, a federal magistrate ruled on Wednesday.

Ahmed Abu Khatallah appeared at a brief detention hearing in federal court in Washington where he's accused of providing material support to terrorists.

Court documents released on the eve of the hearing allege he "conspired to participate and then participated" in the September 11, 2012, attack on the American outpost in eastern Libya that killed Ambassador Christopher Stevens and three other Americans.

He previously pleaded not guilty to the charge that carries a maximum life prison sentence. More are charges are possible.

Abu Khatallah, who is thought to be in his early 40s, was captured earlier this month in Libya and transferred to the United States last weekend.

Authorities contend that he's a senior leader of Ansar al Sharia, whose members were among several militias that participated in the two-pronged armed assault.

Assailants armed with automatic weapons and rocket-propelled grenades first blasted through the main diplomatic mission before setting it ablaze, the court papers said. Stevens and State Department information officer Sean Smith died there. A coordinated mortar assault on a nearby annex killed security officers Tyrone Woods and Glen Doherty.

"The defendant's participation in the attack was motivated by his extremist ideology," prosecutors said in the documents, which also alleged that Abu Khatallah "voiced concern and opposition to the presence of an American facility in Benghazi" days prior to the attack.

Arguing for his continued detention, prosecutors said that Abu Khatallah, since the attack, "has continued to make efforts to target American personnel and property" and "discuss with others his deadly and destructive intentions," prosecutors said.

But defense lawyers contend the Justice Department hasn't provided evidence to support the case.

CNN's Pamela Brown asked lead prosecutor Michael DiLorenzo about the claims from Abu Khatallah's camp regarding pre-trial discovery. He responded that prosecutors would try the case in court.

The Benghazi attack has become a political flashpoint with Republicans, especially, questioning security protections beforehand, the U.S. response during the assault, and the Obama administration's slow-to-evolve public explanation of what transpired.

GOP members also are scrutinizing how Hillary Clinton handled the matter. She oversaw U.S. diplomacy at the time as secretary of state, and questions about her responses and decisionmaking endure as she considers a run for president.