NEW YORK (Reuters) - A failed car bombing in New York's teeming Times Square may involve more than one person and could have international ties, law enforcement sources said on Monday.

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The sport utility vehicle used in Saturday's attempted attack was recently sold to a man described as Hispanic or Middle Eastern, the sources told Reuters.

Casualties, damage and chaos would have been certain in Times Square if the crude bomb made of fuel and fireworks had gone off as the theater, shopping and hotel district was packed with people on a warm weekend evening.

For New Yorkers who bore the brunt of the September 11 attacks by al Qaeda militants in 2001, the scare was a reminder that their city of 8 million people is under constant threat.

"If anything was made clear on Saturday night, it's that New York is a target," U.S. Senator Charles Schumer, a Brooklyn native, said on Monday as he urged Washington to give the city $30 million to boost security. "We need to do everything in our power to deliver the funding to protect New Yorkers."

Street vendors selling T-shirts and handbags alerted police to the smoking and sparking Nissan Pathfinder that was parked awkwardly with its engine running and hazard lights on near a Broadway theater where Disney's "The Lion King" is performed.

The registered owner of the vehicle told police on Monday he sold it three weeks ago without any paperwork to the 29- or 30-year-old man, the sources said.

The Pathfinder, with a license plate taken from a car now in a repair shop in neighboring Connecticut, contained propane gas cylinders, gasoline cans, fertilizer, fireworks and timing devices when it was found in Times Square.

"I would say that that was intended to terrorize," White House spokesman Robert Gibbs told reporters. "And I would say that whoever did that would be categorized as a terrorist."

The incident had little impact on Monday on a broadly stronger stock market and Treasury bonds stayed lower in a similarly muted reaction, with attention focused on encouraging economic data and reduced anxiety over Greece.

'INTERNATIONAL IN SCOPE'

Police -- who are poring over surveillance camera footage, the Pathfinder and the bomb parts for clues -- are looking for a white man in his 40s captured on video near the vehicle shortly after it was left in Times Square.

As this differs from the description of the car buyer, one law enforcement source said it gave "some credibility to the statement that (investigators) believe there is more than one individual involved and that it is international in scope."

But several officials cautioned against drawing conclusions about who was responsible because the investigation was still in the early stages.

"I can't at this point rule in or out the possibility of international connections," said one senior U.S. intelligence official. "People need to let the facts lead where they will and it's unclear to me that all the facts are in."

New York City Mayor Michael Bloomberg described the failed bomb attack as an "amateurish job" but authorities said the device could have created a deadly fireball had it detonated.

U.S. Attorney General Eric Holder vowed on Monday that those responsible would be arrested.

"We have made really substantial progress. We have some good leads," Holder told reporters in Washington. "We are following a number of other leads as well."

The Taliban in Pakistan said on Sunday it planted the bomb to avenge the killing in April of al Qaeda's two top leaders in Iraq. New York Police Commissioner Ray Kelly and Bloomberg have said there was "no evidence" to support that claim.

But former CIA analyst Bruce Riedel, who oversaw an Obama administration strategy review on Afghanistan and Pakistan last year, cautioned against dismissing a possible role of the Pakistani Taliban in the failed car bomb.

"They have said they want to attack inside the United States," said Riedel, adding there was "a very serious possibility" the incident involved "some Pakistani-American who has never built a car bomb before in his life but who is being coached either by phone or Internet."

Security at airports on the U.S. East Coast was boosted after the Times Square scare, a Department of Homeland Security official said.

Police said they plan to release a second video, taken by a tourist in Times Square and showing a man running near the scene at about the time of the incident.

Street vendor Duane Jackson is one of several traders lauded as heroes for alerting police to the car just minutes after it was abandoned. President Barack Obama called Jackson, a Vietnam veteran, on Monday to thank him for his vigilance.

(Additional reporting by Jeremy Pelofsky, Adam Entous, Patricia Zengerle, Will Dunham and Deborah Charles in Washington; Editing by John O'Callaghan)