UPDATE 1-Accused Somali pirate pleads not guilty in NY court

* Pirate suspect enters plea through interpreter

* Lawyers seek witnesses to say he is a juvenile (Adds detail throughout)

By Christine Kearney

NEW YORK, May 21 (Reuters) - A Somali teenager accused of holding a U.S. ship captain hostage in the Indian Ocean after an attempted hijacking pleaded not guilty on Thursday to 10 charges, including piracy and kidnapping.

Abduwali Abdukhadir Muse, the sole surviving accused pirate from the foiled bid to hijack the huge U.S. container ship Maersk Alabama, entered his plea at the U.S. District Court in Manhattan.

The slightly built Muse, who prosecutors said acted as the leader of the pirates, appeared in court in a prison uniform and entered his plea in a quiet voice through an interpreter.

His lawyers told the court that he needed an operation for his hand that was injured during the attack, and had been granted little contact with his mother and family in Somalia since being held in U.S. custody.

Prosecutors and representatives for Muse disagree about his age. Outside the courthouse, lawyers said they were looking for witnesses in Somalia to prove Muse is a juvenile after a judge ruled in April he is aged 18 and would be tried as an adult.

The defense lawyers said they had difficulty communicating with Muse and he did not understand why he had been given medication. They said they could not reveal what the medication was for.