A Tunisian man who allegedly met one of the men suspected of plotting to bomb a Canadian train was charged with visa fraud in New York, prosecutors say.
Ahmed Abassi allegedly met Chiheb Esseghaier and attempted to radicalise him, New York prosecutors said.
He came to the US in March and kept contact with an undercover FBI agent before his 22 April arrest, they said.
Mr Esseghaier, 30, and Raed Jaser, 35, are charged with conspiracy to carry out an attack and kill people.
An indictment against Mr Abassi, unsealed on Thursday, alleged he came from Canada and was fraudulently seeking a US work visa in order to “facilitate an act of international terrorism”.
US Attorney for Manhattan Preet Bharara said: “As alleged, Ahmed Abassi had an evil purpose for seeking to remain in the United States – to commit acts of terror and develop a network of terrorists here, and to use this country as a base to support the efforts of terrorists internationally.”
In recorded conversations between the two men, Mr Abassi expressed his desire to “engage in terrorist acts against targets in the United States and other countries”, the justice department said in a statement.
He was arrested at John F Kennedy International Airport, authorities said.
Mr Abassi was also recorded talking about his desire to aid militant groups, including the al-Nusra Front.
That group has been described by the US as a front for al-Qaeda in Iraq, and has gained support in rebel-held parts of Syria.
Canadian media have reported the investigation into Mr Esseghaier and Mr Jaser was launched after a tip-off by a concerned imam in the Toronto Muslim community.
Authorities had been tracking Mr Esseghaier for two years before beginning to investigate the alleged plot in August 2012.
BBC NEWS