US lawmakers will begin debate as early as Tuesday on whether to halt intelligence agencies from spying on millions of Americans, but senior senators warned the effort was "unwise."
The debate comes six weeks after a National Security Agency contractor divulged details of huge programs that collect telephone and Internet data on millions of Americans and foreigners.
A handful of liberal Democrats have joined Tea Party conservatives in the House of Representatives in sponsoring an amendment to halt NSA surveillance of Americans who are not connected to an ongoing probe.
Republican congressman Justin Amash tweeted his thanks to House Speaker John Boehner for bringing the amendment -- which is tacked on to the defense spending bill under review -- up for open debate this week.
"My amendment blocks funding of #NSA's collection of personal data if that data does not pertain to a person under investigation," Amash said on Twitter.
In addition to limiting the government's ability under the Patriot Act to collect such information, the bill also requires that secret Foreign Intelligence Surveillance Act (FISA) court opinions be made available to Congress and that summaries of those opinions be made public.
House Democrats John Conyers and Jared Polis joined Amash's amendment, which they said "makes sure that innocent Americans' information isn't needlessly swept up into a government database."
"The recent NSA leaks indicate that the federal government collects phone records and intercepts electronic communications on a scale previously unknown to most Americans," they added.
But Democrat Dianne Feinstein, chair of the powerful Senate Intelligence Committee, and the panel's ranking Republican Saxby Chambliss, issued a curt warning about the amendment Tuesday.
The two Senators assured lawmakers the data-mining program is under "strict controls" and has been authorized by all three branches of government.
Ever since details of the classified programs were leaked in early June, Congress has "explored how the program can be modified to add extra privacy protections without sacrificing its effectiveness" in rooting out terror suspects, they said.
"Any amendments to defund the program on appropriations bills would be unwise."
Last week, a House Judiciary Committee hearing saw lawmakers blast intelligence agencies for trampling on privacy rights, saying the collection of bulk phone data was beyond the limits of the US Constitution as well as of legislation adopted by Congress.
They warned that the government's far-reaching surveillance activities would be on the chopping block unless reforms were implemented.
Officials insisted the government was conducting only a relatively small number of searches through the phone data, despite the large volume of telephone records collected, and that it was barred from looking for any information on crimes unrelated to terror threats.