Faruq Khalil Muhammad 'Isa entered the plea in federal court in Brooklyn, where a magistrate judge jailed him without bail on charges of conspiring to kill Americans and providing material support to terrorists without ever leaving Canada.
Muhammad 'Isa, who also goes by Sayfildin Tahir Sharif, is a 36-year-old Canadian citizen and Iraqi national. He was arrested in 2011 on a U.S. warrant after an investigation by authorities in New York, Canada and Tunisia. He was held in Edmonton until he lost an extradition fight claiming the U.S. had no jurisdiction in the case and was brought to New York City on Friday.
Earlier this month, the Supreme Court of Canada declined to hear the arguments of his lawyers that RCMP didn't allow him access to a lawyer or interpreter the day of his arrest, and that he didn't understand what was going on.
In a statement, U.S. Attorney Loretta Lynch said the case "demonstrates to those who orchestrate violence against our citizens and our soldiers that there is no corner of the globe from which they can hide from the long reach of the law." One of Muhammad 'Isa's American defence attorneys, Chase Scolnick, declined comment.
Muhammad 'Isa is an ethnic Kurd who was born in Iraq but moved to Toronto as a refugee in 1993. Four years later, he became a Canadian citizen.
An extradition request cited wiretap evidence and an interview of Muhammad 'Isa that U.S. authorities claim link him to the terror network. Authorities say the group used a suicide bomber to detonate an explosives-laden truck outside the gate of the U.S. base in Mosul, Iraq, on April 10, 2009, killing the soldiers, and staged a separate suicide bombing on an Iraqi police station on March 31, 2009, that killed seven people.
During the interview, Muhammad 'Isa admitted he corresponded by email with two of the terrorists while they were in Syria, and that they were on a mission to kill Americans, the paperwork said. The documents allege he corresponded with "facilitators" who were trying to get the attackers into Iraq, and wired one of them $700.
On wiretaps, Muhammad 'Isa was overheard discussing with someone in Iraq how he used code words when discussing the Iraq operation, the papers said.
"For example, when I want to name the brothers, I say the farmers — because they plant metal and harvest metal and flesh," the papers quoted him as saying. He also explained that he used the term "married" to mean "in the afterlife."
U.S. authorities alleged that the day after the attack on the U.S. base, Muhammad 'Isa asked in an electronic communication, "Did you hear about the huge incident yesterday? Is it known?" He also identified the bomber as "one of the Tunisian brothers," to which a facilitator responded, "Praise God."
Muhammad 'Isa told investigators in the interview that by "huge incident" he meant an explosion, the papers said.
He was arrested in 2011 at an Edmonton apartment where he lived with his girlfriend and her children.
Canada's justice minister granted extradition in 2013 after receiving assurances from the U.S. that he wouldn't face the death penalty if convicted.
His lawyers asked the Supreme Court to stop his extradition after the Alberta Court of Appeal upheld it in August.
They argued that in addition to RCMP failing to allow their client access to a lawyer or interpreter the day of his arrest, they said allegations against him came from three people — including his brother — who were tortured by investigators in Iraq.
The Appeal Court agreed the extradition judge should not have outright rejected the torture allegations by Sharif's brother. It also said the judge should have asked the federal attorney general to disclose evidence about the brother's interrogation or strike the evidence from the deportation proceedings.
Still, the appeal judges wrote, those failures weren't enough to stop the extradition because it said the information obtained from that interview constituted a "minute part of the information contained in the record of the case."
The Appeal Court also said Sharif had access to a lawyer after his arrest, was aware of his right to silence and was not intimidated by investigators.
As usual, the Supreme Court did not give reasons for its decision not to hear the case.
If convicted, Muhammad 'Isa could face a maximum sentence of life imprisonment.
No date was set for another court appearance.
With files from The Canadian Press