Abde Wale Abdul Kahhir Muse appeared briefly in court
A Somali man arrested after a US captain was kidnapped has pleaded not guilty to 10 charges in a New York court, including piracy.
Abde Wale Abdul Kadhir Muse was also charged with holding a hostage for ransom and armed hijacking.
He spoke through a translator during the brief appearance. His next hearing was set for 17 September.
His lawyers said they had difficulty communicating with him, and that he was "confused" about the situation.
Defence lawyer Phil Weinstein also said "they are giving him medications that he doesn't understand", AFP news agency reported.
It was unclear what the medication was for.
Mr Muse's mother has said he is only 16 years old but prosecutors argue he is over 18 and a judge last month ruled he should be tried as an adult.
He is believed to be the first person to face piracy charges in the US in over a century. He faces life in prison if convicted.
Prosecutors have accused Mr Muse of being the ringleader of a pirate gang which boarded a container ship, the Maersk Alabama, on 8 April and took Capt Richard Phillips hostage in a lifeboat.
After a five-day stand-off, US Navy marksmen killed three of the pirates and captured Mr Muse, who had gone aboard a US warship, allegedly to demand a ransom.
Mr Muse's mother has previously told the BBC's Somali service her son is completely innocent.
Heavily-armed pirates operating off the coast of Somalia carry out regular attacks on shipping in recent weeks in one of the world's busiest sea lanes, despite patrols by the US and other navies.
Shipping companies last year handed over about $80m (£54m) in ransom payments to the gangs.