Mark Kelly, the husband of former Rep. Gabrielle Giffords (R-Ariz.), on Sunday warned GOP lawmakers not to filibuster efforts to pass gun control in the Senate.

"It is important to take action and the American people are demanding action now," said Kelly on “Fox News Sunday.” 

Kelly’s comments came in response to five Senate Republicans — Sens. Marco RubioMarco Antonio RubioRyan pledges 'entitlement reform' in 2018 Richard Gere welcomes lawmakers' words of support for Tibet Dem lawmaker gives McConnell's tax reform op-ed a failing grade MORE (Fla.), Rand PaulRandal (Rand) Howard PaulLexington mayor launches bid for Congress Trump-free Kennedy Center Honors avoids politics Meet the Iran hawk who could be Trump's next secretary of State MORE (Ky.), Ted CruzRafael (Ted) Edward CruzDebbie Wasserman Schultz marks 10 years as breast cancer survivor Foreign agent registration is no magical shield against Russian propaganda Let Trump be Trump and he'll sail through 2020 MORE (Texas), Mike LeeMichael (Mike) Shumway LeeSupreme Court takes on same-sex wedding cake case House approves motion to go to tax conference — with drama Trump really will shrink government, starting with national monuments MORE (Utah) and James InhofeJames (Jim) Mountain InhofeGOP senator on backing Moore: ‘It’s a numbers game’ Overnight Energy: Panel advances controversial Trump nominee | Ex-coal boss Blankenship to run for Senate | Dem commissioner joins energy regulator Senate panel advances controversial environmental nominee MORE (Okla.) – who said last week that they will filibuster any additional gun restrictions, as Senate Majority Leader Harry ReidHarry ReidBill O'Reilly: Politics helped kill Kate Steinle, Zarate just pulled the trigger Tax reform is nightmare Déjà vu for Puerto Rico Ex-Obama and Reid staffers: McConnell would pretend to be busy to avoid meeting with Obama MORE (D-Nev.) prepares to move a gun bill.

Kelly said that the bill, which expands background checks at its core, along with measures to punish straw purchasers of firearms and provide more funds for school safety, was supported by the public.

"They should listen to their constituents and certainly shouldn't be getting in the way of the process, which is to debate the bill and to vote on the bill," Kelly said.

"It doesn't make any sense and I imagine that at some point, if they actually do this, their constituents will hold them accountable for those actions," he added.

The former astronaut has been at the forefront of the issue since his wife was shot in the head more than two years ago.

Kelly said that 94 percent of Rubio's constituents support a universal background check, while 83 percent in Kentucky back the concept.

The bill includes language crafted by Democratic Sen. Charles SchumerCharles (Chuck) Ellis SchumerAmerica isn't ready to let Sessions off his leash Schumer celebrates New York Giants firing head coach: ‘About time’ GOP should reject the left's pessimism and the deficit trigger MORE (N.Y.) after efforts to craft a bipartisan proposal on background checks faltered amid GOP concerns that the measure could lead to a federal database of gun owners. 

Kelly acknowledged the difficulties finding GOP support, but said he was optimistic an accord could be reached. "This is certainly an issue that can be worked on," he said.

"We have a lot of smart members in the Senate and I think they can figure out a compromise on this issue."

Kelly called expanded background checks "the most commonsense thing we can do to prevent criminals and the mentally ill from gaining access to firearms."

Kelly said 40 percent of all gun purchases happen without a background check and those sales could account for many of the weapons which fall into the hands of the mentally ill or criminals.

"It's crazy that we have this system where responsible owners get a background check and the option to avoid one is available for anybody who doesn't want to do it. It's a crazy system," Kelly said.

He demanded that any bill produced by the Senate apply background checks to purchases made at gun shows and through private sellers, including the Internet.

"The system currently works with federally licensed firearms dealers so there is no reason that same system can't work with the gun show and the private seller," he said.

While Republicans have expressed opposition to broader background checks, there is a push by a bipartisan group of senators to ensure that mental health information is submitted into the system and can be used by gun sellers.

Kelly acknowledged that the National Rifle Association (NRA) has a point when it argues that the current background check system is ineffective without a beefed up system that includes better access to mental health information and other records.

"They absolutely have a point they are right on that issue," he said. "We need to encourage states to include the mental health records."

In fact, under an improved system, Kelly argued, wife's shooter Jared Loughner would have been turned down from making a purchase.

He vowed to work with the Senate to reach a compromise on language that ensures that the legislation doesn't create of a national registry, which some opponents argue would lead to gun confiscations. He said records would remain at a gun store and would not be registered with the federal government.

Sen. Chuck GrassleyCharles (Chuck) Ernest GrassleyGrassley blasts Democrats over unwillingness to probe Clinton GOP and Dems bitterly divided by immigration Thanks to the farm lobby, the US is stuck with a broken ethanol policy MORE (R-Iowa) is crafting an alternative Republican gun control bill that would not include a universal background check but would crack down on gun trafficking and beef up school safety.

Even though support for broader legislation has slipped somewhat since the Newtown massacre in December, Kelly argued that a majority of people — 92 percent of those polled overall and 74 percent of NRA members — want, at the very least, stricter background checks.

"I would hope, at some point, that the leadership of the NRA would just listen to their membership on this issue," he said.

While Kelly said the NRA has done a good job of controlling the debate "one thing that is different now is the fact that we had 20 first-graders murdered in a classroom along with six educators. That's unacceptable."