WASHINGTON (AP) — Congress' easy renewal of an expiring ban on undetectable plastic guns belies the larger reality that one year after the horrific school shooting in Newtown, Conn., major new firearms restrictions have little chance of enactment anytime soon.

Lawmakers took an easy step Monday when the Democratic-run Senate unanimously gave final congressional approval to a bill adding another decade to the prohibition against guns that can slip by airport metal detectors and X-ray machines. The National Rifle Association, which has helped scuttle firearms restrictions this year, did not oppose the extension.

Without action, the ban would have expired Tuesday. The Republican-led House approved the bill last week.

But the NRA did oppose an effort by Sen. Chuck Schumer, D-N.Y., and other Democrats to strengthen the law by requiring plastic firearms to have a permanent metal piece. Senate Republicans defeated that proposal by rejecting a request by Schumer to push it through the Senate unanimously.

Some plastic firearms technically obey the quarter-century-old law with a detachable metal part that can be slipped off to evade airport security. Democrats said the stricter language was needed in an era when improved and increasingly accessible 3-D printers can produce functioning guns.

"It's time that we recognize that the future is here, plastic guns are real," said Sen. Chris Murphy, D-Conn.

President Barack Obama, traveling to Africa for ceremonies honoring the late South African president Nelson Mandela, signed the bill before midnight using a remote signing device called an autopen, the White House said.

Monday's vote came five days before the first anniversary of the nightmare at Newtown's Sandy Hook Elementary School, where a gunman murdered 20 children and six staffers before killing himself.

In the year since, Congress has approved no new gun curbs, even though Obama and Democratic House and Senate leaders made such restrictions a top agenda item.

Their major defeat was last April's Senate rejection of expanded background checks for firearms buyers, which are designed to keep weapons from criminals and the mentally ill.

Also defeated were proposed bans on assault weapons and large-capacity ammunition magazines. None of the plans ever came to votes in the House.

That has left the gun control movement divided, with some wanting to continue pressing those issues while others prefer settling for more modest gains, such as strengthening mental health programs.

Monday's brief Senate debate underscored the divisions — and mistrust — between the two parties on the issue.

Sen. Charles Grassley of Iowa, top Republican on the Senate Judiciary Committee, suggested that Schumer's effort to tighten the curb might threaten technologies used by legitimate gun makers. He said lawmakers should study the issue, but added that Schumer's recent introduction of his bill showed "the real objectives were things other than just getting an extension."

Schumer said he had "no ulterior motive" and expressed optimism about reaching compromise with Grassley. But Sen. Sheldon Whitehouse, D-R.I., used stronger language, saying the outcome illustrated a city where extremists often "force common sense to yield to their ideology."

Underscoring the issue's political sensitivity, both of Monday's Senate votes were on unanimous consent requests. That meant any single senator could scuttle the proposals by objecting.

It also meant the votes were by voice and that no individual senators' votes were recorded. For a handful of Democratic senators seeking re-election next year in GOP-leaning states, the day's votes could have been difficult.

Plastic guns were in their infancy when President Ronald Reagan and Congress first enacted the ban against undetectable firearms in 1988, and when it was renewed in 1998 and 2003. But such weapons have become a growing threat and can now be produced by 3-D printers, which are becoming better and more affordable.

Supporters of tightening the rules say the 10-year renewal helps the gun lobby because it reduces Democrats' ability to revisit the issue.

With Saturday's Newtown anniversary approaching, Rep. Tim Murphy, R-Pa., a psychologist, plans to announce legislation Thursday aimed at boosting federal mental health programs, including treatment, research and training for workers who respond to emergencies.