The influential chairwoman of the Senate intelligence committee said on Tuesday that the National Security Agency’s bulk collection of American phone records, savaged by a federal judge a day earlier, was not “indispensable” for preventing terrorism.

In an interview with MSNBC on Tuesday, senator Dianne Feinstein, a California Democrat who has been a staunch supporter of the National Security Agency, urged the supreme court to determine its constitutionality.

“I’m not saying it’s indispensable,” Feinstein said. “But I’m saying it is important, and it is a major tool in ferreting out a potential terrorist attack.”

Her assessment came a day after Monday’s dramatic ruling from Judge Richard Leon of the US district court for the District of Columbia, who doubted both the constitutionality of the bulk phone records collection and its necessity to stop terrorist attacks.

In a ruling dripping with impatience for the NSA, Leon noted that the Obama administration and the NSA did not actually argue to him that the bulk collection of American phone metadata “actually stopped an imminent terrorist attack,” but instead that it was “faster than other investigative methods might allow.”

The difference helped informed Leon’s decision that the program was very likely unconstitutional, and would have left James Madison, the former US president and constitutional architect, “aghast.”

During the six months since Edward Snowden first disclosed the extent of NSA bulk surveillance, Feinstein has been a crucial Capitol Hill ally for the embattled agency. In television interviews and congressional hearings, she has cited it as a critical tool for detecting terrorism. She is the architect of a bill that would bolster the bulk phone records collection beyond what the NSA currently performs – a bill that stands as the chief competitor to a legislative push aimed at ending the bulk collection.

“The collection of phone numbers, which can be run when a terrorist target in another country calls an American number, is something in my view which protects this country,” Feinstein said in October.

“We would place the nation in jeopardy if we were to end these two programs,” she said in a July hearing that discussed both the NSA’s bulk phone records collection and its mass dragnets on foreign telephone and internet communications.

In her MSNBC interview on Tuesday, Feinstein offered a subtler defense.

“It is my belief we live in a world with serious jeopardy to this nation. And those of us on the intelligence committee see this frequently. Therefore, this program, in conjunction with other programs, helps keep this nation safe,” Feinstein told MSNBC’s Andrea Mitchell.

To Mitchell and in a press release issued shortly afterward, Feinstein said that other judges have blessed the constitutionality of the domestic call data program, and urged the US’ highest court to settle the issue.

“Only the supreme court can resolve the question on the constitutionality of the NSA’s program,” Feinstein said in her statement.

“I welcome a supreme court review since it has been more than 30 years since the court’s original decision of constitutionality, and I believe it is crucial to settling the issue once and for all. In the meantime, the call records program remains in effect.”

The ACLU has a similar case pending before the southern district of New York that seeks to get at the constitutionality of bulk domestic call data collection. Leon invited the government to reply to his ruling, indicating that his will not be the last word on its constitutionality.

John Conyers, a Michigan Democrat on the judiciary committee who opposes bulk collection of phone data, called Leon’s ruling a “turning point” on Tuesday.

“United States district court Judge Leon’s ruling yesterday that this program is ‘likely unconstitutional’ marks a turning point in our efforts to restore the civil liberties that have eroded since the early days of the Bush administration,” Conyers said in a statement.

“Judge Leon has laid bare the questionable constitutional underpinnings of bulk collection and warrantless mass surveillance. Congress must now intensify its examination of the NSA’s telephone metadata program and other surveillance programs like it, and hold legislative hearings aimed at curing their constitutional defects.”