WASHINGTON (AP) -- Congress is racing toward renewing a 25-year-old prohibition against firearms that can evade metal detectors and X-ray machines, just days before the ban expires. But with 3-D printers increasingly able to produce plastic weapons, many Democrats, gun control advocates and law enforcement officials say the restrictions must be tightened.
The Republican-led House was expected to approve a 10-year extension of the ban on Tuesday. Reluctant to oppose renewal and anger allies, Democrats are expected to back it strongly, despite their preference to also require permanent metal components that would make plastic firearms more detectable.
"We can't let a minute or hour or day go by without having a renewal" of the ban, said Brian Malte, a director of the Brady Campaign to Prevent Gun Violence. The group's strong concerns about the availability of plastic guns are "no reason to hold up renewal," he said.
The Democratic-run Senate returns from a two-week Thanksgiving break next Monday, the day before the ban expires. Sen. Chuck Schumer, D-N.Y., said he will seek fast approval of a measure renewing the ban and tightening the restrictions.
"The House bill is better than nothing, but it's not good enough," Schumer said Monday. He and other critics contend the current law allows for detachable metal parts that can be removed before a gun is passed through a metal detector.
But many believe the Senate will then accept the House bill, thanks to the imminent deadline and the eagerness of Democratic senators seeking re-election next year in GOP-leaning states to avoid difficult votes in a fresh battle over gun control.
The measure is being debated in the shadow of the first anniversary of the massacre last Dec. 14 of 20 first-graders and six staffers at Sandy Hook Elementary School in Newtown, Conn. Those shootings prompted a drive by President Barack Obama and his gun control allies to expand background checks for firearms buyers and other restrictions, which Senate Republicans squelched last April.
The National Rifle Association, which helped defeat last spring's background check measure, has said nothing publicly about whether it supports extending the ban on undetectable firearms.
But congressional aides and lobbyists say the group supports the renewal but opposes efforts to tighten the curbs. A longer renewal would limit Democrats' opportunities to use bills extending the ban to include other gun restrictions.
NRA officials did not answer repeated efforts to reach them.
In a letter to lawmakers last month, the smaller National Shooting Sports Foundation - representing the nation's gun-makers and retailers - said it backs the extension but opposes added restrictions on undetectable guns.
"We are always concerned that laws and regulations do not hamper the ability of our members to take advantage of technological advancements," the group wrote.
The conservative Gun Owners of America opposes the extension, saying such laws wouldn't stop criminals intent on printing weapons.
"They've just spent all year trying to effectively destroy the gun lobby," Mike Hammond, legislative counsel of the small group, said of Democrats. "So why in heaven's name, given this intransigence, should we give them this Christmas present?"
The ban was first enacted in 1988 under President Ronald Reagan, when today's computer and weapons technologies were in their early stages. It was renewed in 1998 and 2003.
Fast forward to 2013, a world where 3-D printers can spray repeated, thin layers of plastic or other materials to create objects from toys to automobile parts to medical devices. They are being used increasingly by companies, researchers and hobbyists, and the technology is constantly improving.
The use of 3-D printers to make guns received heightened attention in May when Cody Wilson, then a University of Texas law student, posted blueprints online for using the printers to make the Liberator pistol, which he says he designed.
Wilson, founder of Defense Distributed, a nonprofit that advocates the free distribution of information on 3-D printed weapons, was ordered by the State Department to take down the instructions after two days because of allegedly violating arms export controls, he said.
At that point, the plans had already been downloaded more than 100,000 times and they remain available on file-sharing websites, he said.
"If you want to do this, it's plainly obvious there's no one standing between you, your computer and your 3-D printer. Anyone can make this gun," Wilson said Monday.
The Bureau of Alcohol, Tobacco, Firearms and Explosives says 3-D printers can cost from $1,000 to $500,000 but can also be leased.
"There are people who will go to any expense, there are groups who will go to any expense if the result is an undetectable firearm," said James Pasco, executive director of the Washington office of the Fraternal Order of Police, representing law enforcement officers.
Earlier this year, ATF tested two guns made from different plastics using Wilson's Liberator design. While one exploded when fired, the other shot eight rounds before ATF halted the test.
"The undetectable firearm threat has become real," agency spokesman Timothy Graden said in an emailed statement.
The expiring law forbids firearms that aren't spotted by airport X-ray screening machines or metal detectors. To meet that requirement, today's plastic guns often come with a metal part that can be detached and isn't necessary for the weapon to function.
The GOP-written House measure would extend that language for another decade.
A bill by Rep. Steve Israel, D-N.Y., would require that such weapons have permanently attached working parts, such as the cylinder, containing at least 3.7 ounces of metal. Schumer, Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., and Sen. Bill Nelson, D-Fla., are working on similar legislation.
On Nov. 21, Sen. Jeff Sessions, R-Ala., blocked a Schumer request for immediate, unanimous Senate approval of a one-year extension of the ban. Tensions were high because earlier that day, Democrats had muscled through changes making it harder for Republicans to block Obama nominations.
Later, Iowa Sen. Charles Grassley - top Republican on the Senate Judiciary Committee - characterized Schumer's abrupt request as "playing politics with public safety." He said Republicans preferred a longer renewal.