WASHINGTON — An analysis of 225 terrorism cases inside the United States since the Sept. 11, 2001, attacks has concluded that the bulk collection of phone records by the National Security Agency “has had no discernible impact on preventing acts of terrorism.”

In the majority of cases, traditional law enforcement and investigative methods provided the tip or evidence to initiate the case, according to the study by the New America Foundation, a Washington-based nonprofit group.

The study, to be released Monday, corroborates the findings of a White House-appointed review group, which said last month that the NSA counterterrorism program “was not essential to preventing attacks” and that much of the evidence it did turn up “could readily have been obtained in a timely manner using conventional court orders.”

Under the program, the NSA amasses the metadata – records of phone numbers dialed and call lengths and times – of virtually every American. Analysts may search the data only with reasonable suspicion that a number is linked to a terrorist group. The content of calls is not collected.

The new study comes as President Barack Obama is deliberating over the future of the NSA’s bulk collection program. Since it was disclosed in June, the program has prompted intense debate over its legality, utility and privacy impact.

Senior administration officials have defended the program as one tool that complements others in building a more complete picture of a terrorist plot or network. And they say it has been valuable in knocking down rumors of a plot and in determining that potential threats against the United States are nonexistent. Director of National Intelligence James Clapper calls that the “peace of mind” metric.

In an opinion piece published after the release of the review group’s report, Michael Morell, a former acting CIA director and a member of the panel, said the program “needs to be successful only once to be invaluable.”

The researchers at the New America Foundation found that the program provided evidence to initiate only one case, involving a San Diego cabdriver, Basaaly Moalin, who was convicted of sending money to a terrorist group in Somalia. Three co-conspirators were also convicted. The cases involved no threat of attack against the United States. “The overall problem for U.S. counterterrorism officials is not that they need vaster amounts of information from the bulk surveillance programs, but that they don’t sufficiently understand or widely share the information they already possess that was derived from conventional law enforcement and intelligence techniques,” said the report, whose principal author is Peter Bergen, director of the foundation’s National Security Program and an expert on terrorism.

In at least 48 instances, traditional surveillance warrants obtained from the Foreign Intelligence Surveillance Court were used to obtain evidence through intercepts of phone calls and emails, said the researchers, whose results are in an online database.

More than half of the cases were initiated as a result of traditional investigative tools. The most common was a community or family tip to the authorities. Other methods included the use of informants, a suspicious-activity report filed by a business or community member to the FBI, or information turned up in investigations of non-terrorism cases.

But Richard Clarke, a member of the White House review panel and a former White House counterterrorism adviser, said he thinks the NSA can use traditional methods – such as obtaining a court order – to obtain data as part of counterterrorism investigations.

“Although we might be safer if the government had ready access to a massive storehouse of information about every detail of our lives, the impact of such a program on the quality of life and on individual freedom would simply be too great,” the group’s report said.