The father, Anzor Tsarnaev, and Dzhokhar arrived in the US on a tourist visa in April 2002 and applied for political asylum, federal law enforcement officers told the New York Times.

BBC: Profile: Dzhokhar and Tamerlan Tsarnaev

The compelling argument is that out of 50, 000 US graduate school and PhD graduates annually, 17, 000 return back to their homeland because no appropriate visa option exists for them to stay in the US to run a startup or take on engineering jobs.

FORBES: Immigration Reform Will Get You Cash

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".

BBC: Tunisian held in New York over Canada train bomb plot