But the entire plot, which began after the man, Quazi Mohammad Rezwanul Ahsan Nafis, came to the United States in January, unfolded under the surveillance of the Federal Bureau of Investigation and the New York Police Department as part of an elaborate sting operation, according to court papers.
Mr. Nafis told an F.B.I. informer in July that he had overseas connections to Al Qaeda, according to a criminal complaint unsealed Wednesday afternoon in Federal District Court in Brooklyn.
Mr. Nafis, the complaint said, had been trying to recruit people to form a terrorist cell and sought out Qaeda contacts to help him carry out an attack. One of the people he tried to recruit was the F.B.I. informer, who later introduced him to an F.B.I. undercover agent, according to the complaint.
“The defendant came to this country intent on conducting a terrorist attack on U.S. soil and worked with single-minded determination to carry out his plan,” said Loretta E. Lynch, the United States attorney in Brooklyn, who announced the charges along with officials from the F.B.I. and the New York Police Department. “The defendant thought he was striking a blow to the American economy. He thought he was directing confederates and fellow believers. At every turn, he was wrong, and his extensive efforts to strike at the heart of the nation’s financial system were foiled by effective law enforcement.”
Mr. Nafis was charged with conspiring to use weapons of mass destruction and providing material support to Al Qaeda; he could face up to life in prison if convicted. He was expected to appear in court in Brooklyn later on Wednesday.
A lawyer for Mr. Nafis, Heidi C. Cesare, could not be reached immediately after his arrest.
“Attempting to destroy a landmark building and kill or maim untold numbers of innocent bystanders is about as serious as the imagination can conjure,” said Mary Galligan, the acting assistant director of the F.B.I. office in New York. “It is important to emphasize that the public was never at risk in this case, because two of the defendant’s ‘accomplices’ were actually an F.B.I. source and an F.B.I. undercover agent.”
The undercover agent supplied Mr. Nafis with what Mr. Nafis believed to be 20 50-pound bags of explosives, but which were, in fact, inert, according to the complaint. Mr. Nafis bought components for the bomb’s detonator and surveyed the target in Lower Manhattan on a number of occasions, the complaint said. He repeatedly told the undercover agent that the plan was his own and that he had come to the United States to carry it out.
On Wednesday morning, Mr. Nafis met the undercover agent and drove to a warehouse where Mr. Nafis put together what he believed to be the 1,000-pound bomb, using the 20 bags of an unnamed explosive.
On the way to the warehouse, Mr. Nafis told the agent that he had a “Plan B” — a suicide bombing — in the event that his primary plan to bomb the bank was interrupted by the authorities.
After Mr. Nafis assembled the bomb, the two men drove to the New York Federal Reserve Bank, on Maiden Lane and William Street in Lower Manhattan, about two blocks from Wall Street. Mr. Nafis, the complaint said, armed the device while they were en route to the bank, a 22-story building that resembles an impregnable fortress.
Mr. Nafis and the undercover agent parked the van outside the bank and walked to a nearby hotel, where Mr. Nafis recorded a video statement addressed to the American people that he planned to distribute after the attack. In the statement, he said, “We will not stop until we attain victory or martyrdom.”
Then he tried over and over again to detonate the bomb to no avail, and agents arrested him.
The plot is the latest to fit a model in which, in the process of flushing out people they believe present a risk of committing terrorist acts, federal law enforcement officials have played the role of terrorist enabler — providing targets with encouragement, guidance, money and even, the subjects of sting operations are led to believe, the materials needed to carry out an attack. Though these operations have almost always held up in court, they have come under increasing criticism from those who believe that many of the targets, even some of those who openly espoused violence, would have been unable to execute such plots without substantial assistance from the government.
Both F.B.I. leaders and federal prosecutors have defended the approach as valuable in finding and stopping people predisposed to commit terrorism.