Minh Quang Pham, 29, was charged with traveling from Britain to Yemen in December 2010, where federal prosecutors said he pledged allegiance to al Qaeda in the Arabian Peninsula (AQAP).
The United States considers the Yemen-based group as a terrorist organization.
Pham spent a year in Yemen before returning to Britain, according to an indictment unsealed on Friday in Manhattan federal court.
While in Yemen, Pham is accused of receiving "military-type" training and of helping with the group's online propaganda. While in Yemen, he also worked alongside two unidentified U.S. citizens, the indictment said.
Pham, who is in custody in Britain, is charged with five criminal counts, including conspiracy to provide material support to a terrorist group. He faces a mandatory minimum of 40 years in prison if convicted on all counts.
It was not immediately clear if and when he would be brought to New York to face the U.S. charges.