NEW YORK — A Somali teenager accused of leading a pirate attack on an American cargo ship off the coast of Africa pleaded not guilty today to piracy charges.

Abdiwali Abdiqadir Muse, 18, entered the plea during a brief appearance in U.S. District Court in Manhattan, where his lawyers noted he has been kept in solitary confinement since he was brought to the United States last month.

Authorities said Muse was the only surviving pirate among a group that attacked the U.S.-flagged Maersk Alabama on April 8. He was captured April 12 as U.S. military snipers fired on a group holding the cargo vessel's captain hostage. The captain, Richard Phillips, has since returned to his home in Underhill, Vt., to a hero's welcome.

Muse was indicted earlier this week on 10 counts including piracy under the law of nations, conspiracy, hostage taking, kidnapping and possession of a machine gun while seizing a ship by force. If convicted of the most serious charge, he faces a mandatory life sentence.