NEW YORK - The Obama administration gave up on its plan to try the alleged Sept. 11 plotters in Lower Manhattan yesterday, bowing to almost unanimous pressure from New York officials and business leaders to move the terrorism trial elsewhere.

“I think I can acknowledge the obvious,’’ an administration official said. “We’re considering other options.’’

The reversal on trying the accused Sept. 11 terrorists blocks from the former World Trade Center site seemed to come suddenly this week, after New York’s mayor, Michael R. Bloomberg, abandoned his strong support for the plan and said the cost and disruption would be too great.

But behind the brave face that many New Yorkers had put on for weeks, resistance had been gathering steam.

After a dinner in New York on Dec. 14, Steven Spinola, president of the Real Estate Board of New York, pulled aside David Axelrod, President Obama’s closest adviser, to convey an urgent plea: move the planned trial for the Sept. 11 suspects out of Manhattan.

In a series of presentations in recent weeks - to business leaders, local elected officials, and community representatives of Chinatown - New York’s police commissioner, Raymond W. Kelly, laid out his plan for securing the trial: blanketing lower Manhattan with police checkpoints, vehicle searches, rooftop snipers, and canine patrols.

“They were not well received,’’ said one city official.

On Tuesday, in a meeting Bloomberg had with at least two dozen federal judges in their Manhattan courthouse, one judge raised the question of security. The mayor, according to several people present, said he was sure the courthouse could be made safe, but that it would be costly and difficult.

The next day, Bloomberg, who in November hailed the idea of trying Khalid Sheikh Mohammed and four other alleged Sept. 11 plotters in the heart of downtown Manhattan, made clear that he had changed his mind.

Told of the Obama administration’s decision last night, a spokesman for Kelly said, “We were not aware of that.’’

But the spokesman, Paul J. Browne, said of Kelly: “He is of the mind that such a decision would give us some breathing room, but that New York has to remain vigilant because it remains at the top of the terrorist target list.’’

Bloomberg’s remarks Wednesday set off a stampede of New York City officials, most of them Democrats well-disposed toward Obama, who suddenly declared that a civilian trial for the Sept. 11 suspects was a great idea - as long as it didn’t happen in their city.

By yesterday, Justice Department officials were studying other locations, focusing especially on military bases and prison complexes, and no obvious new choice had emerged.

The story of how prominent New York officials seemed to have so quickly moved from a kind of “bring it on’’ bravado to an “anywhere but here’’ stance involves many factors, including a new anxiety about terrorism after the attempted airliner bombing on Christmas Day.

It appears New York officials could not tolerate ceding much of the city to a set of trials that could last for years.

“The administration is in a tricky political and legal position,’’ Julie Menin, a lawyer who is chairwoman of the 50-member Community Board 1 that represents lower Manhattan, including the federal courthouse and ground zero, said of Obama and his Justice Department. “But it means shutting down our Financial District. It could cost $1 billion. It’s absolutely crazy.’’

Menin said the turning point for her came when she heard Kelly’s security plan and cost estimates: hundreds of millions of dollars a year. “It was an absolute game-changer,’’ she said. She wrote a Jan. 17 op-ed article for The New York Times proposing moving the trial to Governor’s Island, off Manhattan; that idea did not catch hold, but the article escalated the outcry to relocate.

When the Justice Department announced in November its plans to try Mohammed and four alleged accomplices blocks from where the World Trade Center stood, Bloomberg hailed the location as not only workable but as a powerful symbol.

“It is fitting that 9/11 suspects face justice near the World Trade Center site where so many New Yorkers were murdered,’’ the mayor said at the time.

It is possible the reversal will call into question the calibrated effort of Obama and his attorney general, Eric Holder, to bring the handling of suspected terrorists out of the realm of military emergency and into the halls of civilian justice. If the message to Al Qaeda in November was that New York City was able to bring justice to those who plotted mass murder, the message of January is far less confident.

“This will be one more stroke for Al Qaeda propaganda,’’ said Bruce Hoffman, a terrorism analyst at Georgetown University. He said the terrorist group may portray the flap over a trial site as “a sign of American weakness,’’ though he said it would be a “debating point rather than a real recruiting tool.’’

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