The White House and congressional backers of the National Security Agency's surveillance program warn that ending the massive collection of phone records from millions of Americans would put the US at risk from another terrorist attack.
With a high-stakes showdown vote looming in the House of Representatives, White House press secretary Jay Carney issued an unusual, nighttime statement on the eve of Wednesday's vote.
The measure by Republican Rep Justin Amash would end the secret program's authority, an action that Carney contended would "hastily dismantle one of our intelligence community's counterterrorism tools."
Gen Keith Alexander, head of the NSA, made a last-minute trip to Capitol Hill on Tuesday (Wednesday NZT) to urge lawmakers to reject the measure in separate, closed-door sessions with Republicans and Democrats. Seven Republican committee chairmen issued a similar plea in a widely circulated letter to their colleagues.
An unlikely coalition of libertarian-leaning conservatives and liberal Democrats says the program amounts to unfettered domestic spying on Americans. Amash and Democratic Rep John Conyers are the chief sponsors of an amendment that would end the ability of the NSA to collect phone records and metadata under the USA Patriot Act unless it identifies an individual under investigation.
Amash said his measure tries to rein in the NSA's blanket authority. Responding to the White House statement, the congressman tweeted late Tuesday: "Pres Obama opposes my (hash)NSA amendment, but American people overwhelmingly support it. Will your Rep stand with the WH or the Constitution?"
Republican leaders allowed the House to consider Amash's amendment to a $598.3 billion (NZ$750.2 billion) defense spending bill for the fiscal year beginning October 1.
The vote on Wednesday would be the first time Congress has weighed in since former NSA systems analyst Edward Snowden leaked documents that revealed that the NSA had collected phone records, while a second NSA program forced major Internet companies to turn over contents of communications to the government.
"This blunt approach is not the product of an informed, open or deliberative process," Carney said.
"We urge the House to reject the Amash amendment, and instead move forward with an approach that appropriately takes into account the need for a reasoned review of what tools can best secure the nation."
Proponents of the NSA programs argue that the surveillance operations have been successful in thwarting potential terrorist attacks, including a 2009 plot to strike at the New York Stock Exchange.
"This bill would basically turn off our ability to find terrorists trying to attack us," said Rep CA Dutch Ruppersberger, the top Democrat on the Intelligence panel.
Rep. Mike Rogers, chairman of the Intelligence committee, joined other Republican chairmen in a letter urging lawmakers to reject the Amash amendment.
"While many members have legitimate questions about the NSA metadata program, including whether there are sufficient protections for Americans' civil liberties, eliminating this program altogether without careful deliberation would not reflect our duty, under Article I of the Constitution, to provide for the common defense," the chairmen wrote.
The debate over privacy and national security has prompted calls and emails to lawmakers, said Republican Rep. Tom Rooney, a member of the Intelligence panel who said members of Congress are facing competing pressures.
The overall defense spending bill would provide the Pentagon with $512.5 billion (NZ$642.2 billion) for weapons, personnel, aircraft and ships plus $85.8 billion (NZ$107.6 billion) for the war in Afghanistan for next budget year.
The bill is $5.1 billion (NZ$6.4 billion) below current spending and has drawn a veto threat from the White House, which argues that it would force the administration to cut education, health research and other domestic programs to boost spending for the Pentagon.
In a leap of faith, the bill assumes that Congress and the administration will resolve the automatic, across-the-board spending cuts that have forced the Pentagon to furlough workers and cut back on training. The bill projects spending in the next fiscal year at $28.1 billion (NZ$35.2 billion) above the so-called sequester level.
In addition to the vote on the Amash amendment, the House also will consider an amendment prohibiting any U.S. funds for military or paramilitary operations in Egypt and barring the administration from arming the Syrian rebels without congressional approval.
On Tuesday the House voted to cut $79 million (NZ$99 million) from the Afghanistan Infrastructure Fund, reducing the amount to the current level of $200 million (NZ$250 million) as projects have been delayed. The House also endorsed the $70.2 million (NZ$88 million) in the bill to study the feasibility for an East Coast missile defense site.
The overall bill must be reconciled with whatever measure the Democratic-controlled Senate produces.