An expiring ban on plastic firearms capable of evading metal detectors and X-ray machines is shaping up to be a tough fight for gun control advocates, as the Senate gets ready to vote on the renewal of the ban, the Associated Press reported.

Monday's vote comes days before the anniversary of the Sandy Hook Elementary shooting, which spurred a push for new federal gun laws that never made it through Congress. According to the AP, the extension of the prohibition on plastic guns for another decade is in response to a growing threat from steadily improving 3-D printers that can produce such weapons.

Gun control supporters seem to be at a disadvantage in their efforts to impose additional, tougher restrictions on plastic firearms - a harsh reminder of their failure to enact any new federal gun curbs in the year since 20 first-graders and six educators were murdered in Newtown, Conn.

The shootings on Dec. 14, 2012 prompted President Barack Obama to push gun control to the top of his domestic agenda, the AP reported. But Congress approved nothing, and gun control supporters face the same uphill struggle in 2014, complicated by internal divisions over what their next step should be.

"The gun lobby still has enormous power in Washington - more, frankly, than I thought they still had," said Sen. Chris Murphy, a Democrat who represented Newtown last year while in the House.

Sen. Chuck Schumer, a leading Democrat, whose effort to try and make plastic guns more detectable by requiring them to have a permanent metal part seems certain to fail Monday. His plan is opposed by Republicans and the National Rifle Association, a powerful gun advocacy group.

The Senate is expected to easily approve a 10-year extension of the ban, which would otherwise expire Tuesday, according to the AP.

A problem with current law on plastic guns is that it lets gun makers meet its requirements by including a metal part that can be easily detached - thus letting the weapon evade screening devices, said Schumer to the AP.

If, as expected, Democrats fail Monday to tighten the restrictions, it will be the latest in a series of setbacks this year.

In a statement last week, the NRA expressed no opposition to renewing the law. But the gun lobby said it would fight any expanded requirements, including Schumer's "or any other proposal that would infringe on our Second Amendment rights" to bear arms, referring to a provision of the U.S. Constitution, the AP reported.

The prohibition was first enacted in 1988 under President Ronald Reagan and easily renewed twice. The House approved a 10-year extension of the ban last Tuesday.