Key U.S. senators pressed the Obama administration on Thursday to clarify language in pending surveillance reform legislation to ensure that it could not be used by intelligence agencies to collect massive amounts of Americans’ personal data.

Taking up a bill passed last month by the House to end the National Security Agency’s bulk collection of phone data, a divided Senate Intelligence Committee questioned senior intelligence officials at a rare open hearing about how effective the bill would be at preserving the NSA’s flexibility in obtaining information to detect terrorist plots and at safeguarding Americans’ privacy.

The administration supports the USA Freedom Act, which passed the House by a nearly 3-to-1 margin. But several committee members said they felt the compromise bill went too far in its reforms and would hamper the NSA’s ability to accomplish its missions. Others said the compromise, worked out with the administration, lacked sufficient civil liberties safeguards. A coalition of major tech firms, including Google and Yahoo, have urged the Senate to strengthen the bill’s privacy and transparency measures.

Committee Chairman Dianne Feinstein (D-Calif.) said she still supported a rival bill that her panel approved in October that would codify the NSA’s authority to continue to collect billions of records about Americans’ phone calls for counterterrorism purposes.

Feinstein said, however, that because the administration and the House both want to end the government’s bulk collection of records, and “in the interest of passing legislation” now, “we must take a close look at the House legislation with a view to its passage, perhaps as amended, in the Senate.”

The NSA maintains a database of hundreds of billions of numbers dialed, times and dates, but not actual content. The bill would end the agency’s ability to do so by amending the Foreign Intelligence Surveillance Act (FISA), which governs domestic surveillance for foreign intelligence purposes.

Its aim, the administration and supporters say, is to outlaw all bulk collection of records by the government, not just of telephone records.

Vice Chairman Saxby Chambliss (R-Ga.) said he thought the bill is “fixing a lot of things that simply are not broken.’’ He said that “swapping the current program out for an untested system may be a pretty bad deal from a national security perspective and for the American people.”

The House bill replaces the NSA’s collection of phone data with a system in which it can seek court orders to direct phone companies to turn over data from a specific number if it has “reasonable articulable suspicion” that the number is linked to a foreign power and also to an authorized investigation.

But Feinstein noted that the bill has stirred concerns over a requirement that the government focus its collection of what is known as a “specific selection term.”

The bill defines a specific selection term as “a discrete term, such as a term specifically identifying a person, entity, account, address, or device, used by the government to limit the scope of the information or tangible things sought.”

By not limiting the definition to a finite set of terms, critics say, the door is open to collection on a broad scale.

“The NSA has shown, time and time again, it will seize on any wiggle room in the law” to enhance its ability to conduct surveillance, said Sen. Mark Udall (D-Colo.).

Deputy Attorney General James Cole countered that the language does not, for instance, contemplate the government obtaining all the phone numbers in a particular zip code.

The wording, he said, is intended to allow for cases in which, say, an unknown suspect is trying to build a bomb using ball bearings and fertilizer. The bill would enable the FBI to obtain sales records from stores in the area that sell ball bearings and fertilizer. “It’s much broader than one specific item, but it’s not all stores in America,” he said.

Sen. Ron Wyden (D-Ore.) noted that the House bill did not ban warrantless searches for the e-mails of Americans whose communications are collected under a separate NSA program targeting foreigners located abroad. He demanded to know how many such searches have taken place since 2011. NSA Deputy Director Rick Ledgett promised to provide a response within two weeks.