The Obama administration acknowledged Thursday that it had attempted, and failed, to build a Twitter-like social media site in Cuba, but insisted that it was part of the Agency for International Development's effort to encourage political discussions, not a covert program to overthrow the government.
Arguments over the purpose of the program, called ZunZuneo, arose after The Associated Press published a detailed article about it on Thursday, based in part on documents from a contractor for the development agency.
One memo said, "There will be absolutely no mention of United States government involvement."
The program ran from 2008 to 2012, when it abruptly ended, apparently because a $1.3 million contract to start up a text-messaging system ran out of money. At the time, about 40,000 Cubans were using ZunZuneo, which The A.P. noted was "slang for a Cuban hummingbird's tweet."
"No business was able to take this idea and utilize it effectively," said Matt Herrick, the agency's spokesman. "So the project ended."
Though early in the day the agency said no private data was collected, on Thursday evening Mr. Herrick said users of the system were allowed to submit personal information voluntarily. "Hardly any did, and the program had no use for it," he said.
At first glance, the program seemed to be in the spirit of many failed efforts by the United States government, dating to the Eisenhower and Kennedy administrations, to destabilize the Cuban government. The idea was to start the system with innocuous messaging, like soccer scores and weather forecasts. The State Department said the hope was that over time it would promote democracy.
By the standards of American efforts in Cuba, ZunZuneo was on the milder side. It did not involve poison cigars for Fidel Castro, or landings by exiles at the Bay of Pigs. It was similarly unsuccessful—having no apparent effect on the Cuban government.
"It was just dumb," Senator Patrick J. Leahy, Democrat of Vermont, who has long argued for lifting the Cuban trade embargo, told MSNBC on Thursday.
He argued that if United States companies were allowed to operate on the island, Twitter would become widely used, even if the Cuban government tried to block it. (A recent effort to ban Twitter in Turkey was mocked before it ended on Thursday.)
However, Senators Robert Menendez, Democrat of New Jersey, and Marco Rubio, Republican of Florida, issued statements supporting the effort to, in Mr. Rubio's words, "bypass the iron grip of the Castro regime."
The State Department said the ZunZuneo effort was part of broader programs to use the Internet and cellphones.
Marie Harf, the deputy spokeswoman at the State Department, said critics who equated ZunZuneo with a covert program did not understand covert programs.
"There was nothing classified or covert about this program," Ms. Harf said. "Discreet does not equal covert. Having worked for almost six years at the C.I.A. and now here, I know the difference."
She said ZunZuneo was an effort to provide the Cuban people with "platforms for expression."
James Lewis, a cyberexpert at the Center for Strategic and International Studies, described the program as "amateur-hour covertness, which is to say that it wasn't very covert."
The issue is an important one because the development agency's workers in repressive countries are often accused of working for the C.I.A. Another contractor working for the United States government, Alan Gross, remains in jail in Cuba after trying to broaden access to the Internet there.
As secretary of state, Hillary Rodham Clinton pushed for many such programs around the world, noting the success of social media in organizing protests in Egypt and Tunisia.
The documents cited by The A.P., which it did not separately publish, made clear that contractors working on the Cuba project wanted to keep their telephone database confidential.
The State Department has long viewed text messaging as a potential instrument of so-called street diplomacy, especially after it was widely used in Iran in 2009 to organize protests against the re-election of Mahmoud Ahmadinejad as president.
—By David E. Sanger of The New York Times