Faisal Shahzad told law enforcement authorities he "received bomb-making training" in Pakistan and admitted his involvement in the failed car-bombing attempt in Times Square, court records show.
Shahzad received his training in the lawless tribal region of Waziristan, where the Pakistani Taliban operates with near impunity, according to a criminal complaint detailing charges against him.
Shahzad faces terrorism and weapons of mass destruction charges at his arraignment Tuesday afternoon after admitting his role and providing investigators with "useful information" since his arrest overnight, Attorney General Eric Holder said earlier Tuesday.
"Based on what we know so far, it is clear that this was a terrorist plot aimed at murdering Americans in one of the busiest places in our country," Holder said in a televised news conference from Washington, D.C.
Officials, among them Holder, Homeland Security Secretary Janet Napolitano, FBI Deputy Director John S. Pistole and NYPD Commissioner Ray Kelly, said the case was quickly solved with "exemplary investigative efforts," the awareness of average citizens and the vigilance of law enforcement officials.
"If successful, it could have resulted in a lethal terrorist attack," Holder said, adding the United States faces a "constant threat from those who wish to do us harm.
"The most dangerous lesson we can draw [from this] is the false impression that this threat no longer exists," he said.
The news conference came after intelligence officials in Pakistan had detained several people in Karachi believed to be connected to Shahzad, according to news reports. "We have picked up a few family members" related to Shahzad, a security official in Karachi told Reuters. He declined to elaborate.
Holder said while he had heard those reports he was not in a position to confirm them.
Government officials said Shahzad, believed to have been living in Bridgeport, Conn., drove a bomb-laden Nissan Pathfinder into Times Square just before 6:30 p.m. Saturday in an attempt to unleash an attack on what Holder called "innocent tourists and theatergoers."
Two street vendors alerted police and mounted officer Wayne Rhatigan of Holbrook quickly responded. That helped avert disaster and saved "hundreds of lives," Obama said.
Federal officials said Shahzad became a naturalized U.S. citizen in April 2009, just before visiting his native Pakistan for five months. Shortly after returning, Shahzad paid $1,300 cash for the Pathfinder.
Kelly said tracing the vehicle to Shahzad began simply enough - when an NYPD detective crawled under the Pathfinder and found its identification number. That enabled investigators to find the owner of record and learn the car was sold to Shahzad.
The net closed on Shahzad late Monday, when he was arrested aboard a Dubai-bound flight on Emirates airlines at Kennedy Airport. Law enforcement officials said Tuesday agents were on the lookout for Shahzad on flight manifests at regional and international airports - but his name only appeared at the last minute because he booked his ticket just before the flight and paid in cash.
Emirates officials said Shahzad's paying cash was a red flag that led the airline to contact law enforcement. The aircraft had left the gate, but returned so Shahzad could be removed.
Pistole said authorities had homed in on Shahzad by Sunday night and had him under surveillance. Customs and Border Protection and other law enforcement agencies were alerted in case he tried to leave the country, Pistole said.
It's not clear if authorities followed Shahzad to the airport.
"The bottom line is, we were able to identify, locate and detain Mr. Shahzad," Pistole said.
Holder said once Shahzad was identified and located, "I was never in any fear that we would lose him."
The flight was delayed about seven hours.
The aircraft and passengers were then rescreened before taking off Tuesday morning, Emirates said in a statement e-mailed to The AP.
A law enforcement official said a 9-mm semiautomatic rifle and ammunition were found in Shahzad's car, parked in a lot at Kennedy.
Federal Bureau of Investigation agents and New York City police detectives from the Joint Terrorism Task Force made the arrest at about 11:45 p.m. after Shahzad was identified by Customs and Border Protection agents at the airport, according to the U.S. attorney's office in New York.
Investigators have not established a connection to the Pakistani Taliban, which claimed responsibility in three videos. Nor had any link been confirmed between Shahzad and any other foreign terrorist groups, a law enforcement official told AP.
"He's claimed to have acted alone, but these are things that have to be investigated," the official said.
Also Tuesday, Obama telephoned Rhatigan and fellow Officer Pam Duffy to commend them on their quick response Saturday.
At a Tuesday morning news conference, Mayor Michael Bloomberg expressed gratitude for the work of investigators who broke the case.
"This was an act that was designed to kill innocent civilians and strike fear into the hearts of Americans," the mayor said. The suspect "failed on both counts."
Bloomberg also emphasized that New York City is a melting pot, and "we're going to keep it that way.
"We will not tolerate any bias or backlash against Pakistani or Muslim New Yorkers," he said.
CAIR, a Muslim civil rights and advocacy group, condemned the attack and welcomed the arrest.
"In no way, shape or form does this attack represent American Muslims or what they stand for as a faith community," CAIR executive director Nihad Awad said in a news release.
Shahzad was reportedly identified with the help of fingerprints found in the Nissan, according to an official who has been briefed by investigators.
The SUV - rigged with firecrackers, propane tanks, gasoline and a nonexplosive grade of fertilizer - was found in Times Square emitting smoke and making popping noises as it idled without a driver on busy West 45th Street near Seventh Avenue.
Since the 9/11 terrorist attacks, the metropolitan area has received about $2 billion in federal anti-terror funding. The Times Square bombing attempt has New York officials calling for even more homeland security funds to prevent another terrorist attack.
With Michael Amon, Alfonso A. Castillo, Anthony M. DeStefano, Reid J. Epstein, Robert E. Kessler, Pervaiz Shallwani, Will Van Sant, and AP.