WASHINGTON >> The Libyan militant accused of masterminding the deadly Benghazi attacks that have become a flashpoint in U.S. politics appeared briefly for the first time in an American courtroom, pleading not guilty Saturday to a terrorism-related charge nearly two weeks after he was captured by special forces.

In a 10-minute hearing held amid tight security, Ahmed Abu Khattala spoke just two words, both in Arabic. He replied "yes" when asked to swear to tell the truth and "no" when asked if he was having trouble understanding the proceeding.

Abu Khattala became the most recent foreign terror suspect to be prosecuted in American courts, a forum the Obama administration contends is both fairer and more efficient than the military tribunal process used at Guantanamo Bay, Cuba. The case was being tried in Washington despite concerns from Republicans in Congress who say he should not be entitled to the protections of the U.S. legal system.

A grand jury indictment handed up under seal Thursday and made public Saturday said Abu Khattala participated in a conspiracy to provide material support and resources to terrorists in the attacks of Sept. 11, 2012, that killed U.S. Ambassador Chris Stevens and three other Americans.

That crime is punishable by up to life in prison. The government said it soon would file more charges against Abu Khattala.

During his initial court appearance, the defendant listened via headphones to a translation of the proceedings. He wore a two-piece black track suit, had a beard and long curly hair, both mostly gray, and kept his hands, which were not handcuffed, behind his back.

He looked impassively at U.S. Magistrate Judge John Facciola for most of the hearing. Abu Khattala’s court-appointed lawyer, Michele Peterson, entered the not guilty plea. Facciola ordered the defendant’s continued detention, but the judge did not say where Abu Khattala would be held.

The U.S. Marshals Service said it had taken custody of Abu Khattalah, who now was confined to a detention facility in the capital region, ending a harried day for the Libyan.

U.S. special forces captured Abu Khattala in Libya two weeks ago, marking the first breakthrough in the investigation. Officials had been questioning Abu Khattala aboard a Navy ship that transported him to the United States. He was flown early Saturday by military helicopter from a Navy ship to a National Park Service landing pad in the city’s Anacostia neighborhood, according to a U.S. official who was not authorized to discuss the transfer publicly and spoke on condition of anonymity.

A U.S. official said Abu Khattala had been advised of his Miranda rights at some point during his trip and continued talking after that. The official wasn’t authorized to discuss an ongoing investigation by name and spoke on condition of anonymity. The nature of those conversations wasn’t immediately clear.

A criminal complaint filed last year and unsealed after Abu Khattala’s capture charged him with terror-related crimes, including killing a person during an attack on a federal facility. A new, single-count indictment will likely be superseded by additional charges, prosecutors say.

The violence in Libya on the 11th anniversary of the Sept. 11 attacks on the World Trade Center and the Pentagon quickly became a political controversy at home.

Republicans accused the White House, as the 2012 presidential election neared, of intentionally misleading the public about what prompted the attacks. The White House said Republicans were politicizing a national tragedy.

Abu Khattala was a prominent figure in Benghazi’s circles of extremists. He was popular among young radicals and lived openly in the eastern Libyan city, spotted at cafes and other public places, even after the Obama administration publicly named him as a suspect.

He is accused of being a member of the Ansar al-Shariah group, the powerful Islamic militia that the U.S. believes was behind the attack.

He acknowledged in an interview with The Associated Press in January that he was present during the storming of the U.S. mission in Benghazi. But he denied involvement in the attack, saying he was trying to organize a rescue of trapped people.

In the attack, gunmen fired rocket-propelled grenades and stormed the mission, with many waving the black banners of Ansar al-Shariah.

The compound’s main building was set ablaze. Stevens suffocated inside and another American was shot dead.

At the time, several witnesses said they saw Abu Khattala directing fighters at the site.

Later in the evening, gunmen attacked and shelled a safe house, killing two more Americans. No evidence has emerged that Abu Khattala was involved in the later attack.

Abu Khattala is one of just a few cases in which the administration has captured a suspected terrorist overseas and interrogated him for intelligence purposes before bringing him to federal court to face charges.

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AP National Security Writer Robert Burns contributed to this report.