WASHINGTON - Exactly how many phone records of Americans does the National Security Agency collect in its massive surveillance program?

Sen. Dick Durbin of Illinois, the No. 2 Democrat in the Senate, tucked a provision into the 2014 fiscal year defense spending bill that would require the NSA to report to Congress - within 90 days after the legislation becomes law - the precise number of phone records collected, the total reviewed by NSA employees and all bulk collection activities, including how much they cost and when they began.

The NSA also would have to provide Congress with a list of potential terrorist attacks that have been thwarted because of information obtained through the sweeping data collection program.

The Senate Appropriations Committee backed the report request on Thursday in voting for the overall bill. It's the first Senate effort aimed at the program since revelations two months ago that the NSA was collecting hundreds of millions of Americans' phone records as part of an effort to combat terrorism.

The disclosure has revived debate over whether secret national security programs encroach on Americans' privacy rights.

The NSA has said that its two surveillance programs - the other sweeps up Internet usage data - have stopped at least 50 terror plots across 20 countries.

"We're talking about some changes in the program, some disclosure in the program that would still keep it in some form as a tool to fight terrorism but would also assure the American people about the limits of its use," Durbin said in a telephone interview on Friday.

The senator was one of several lawmakers - proponents and critics - who met with President Obama and Vice President Joe Biden at the White House on Thursday to discuss the programs.

Durbin said the purpose of his measure is to obtain basic information about the program.

"Just this last week, we did get some information from the NSA about the number of queries in a given year ... and what we do in the bill is to try to make this a more complete disclosure of the volume of collected information," said Durbin, chairman of the Appropriations defense subcommittee and a member of the Judiciary Committee.

Rep. C.A. Dutch Ruppersberger of Maryland, the top Democrat on the House Intelligence Committee, said Friday that "almost everybody" understands that the NSA program is vital. The task in the coming weeks is to make Americans understand that constitutional rights aren't being trampled.

"What we have to do is educate the public, and we have to make some changes to show that so that we can be more open but not give the information to the enemy," Ruppersberger told reporters.

The House Intelligence Committee likely will incorporate some changes in its authorization bill in late September or early October, he said. The counterpart Senate panel and House and Senate Judiciary committees also are likely to act this fall.