A group of Senate Republicans on Monday sent a letter to the acting director of the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) to raise concerns that two of the agency's recently proposed gun rules could set the foundation for a national gun registry.

One of the regulations, referred to as Proposed Rule 2021R-05, requires that licensed manufacturers and importers maintain permanent records of production or importation of firearms, in addition to receipts, proof of sales and other means of distribution, among other initiatives.

"This Proposed Rule would take a significant step toward a national gun registry by requiring FFL [federal firearms license] dealers to maintain personal gun owner information and records of transactions involving firearms, including their makes, models, and serial numbers—forever,” reads the letter from GOP Sens. Josh Hawley (Mo.), Tom Tillis (N.C.), Ted Cruz (Texas) and Tom Cotton (Ark.).

The senators said the second measure, known formally as Proposed Rule 2021R-08, would “reverse years of interpretive guidance and recategorize millions of pistols and AR-15-style firearms as ‘short-barreled rifles.’ ”

As a result, they said the weapons would be placed “under the strict regulatory scheme of the National Firearms Act and making it a federal felony to otherwise possess them.”

The Republicans wrote that the rules are “concerning enough on their face,” while slamming the AFT for its “apparent willingness” to reform firearms policy unilaterally.

“Americans’ rights to keep and bear firearms are safeguarded by the Second Amendment, and the responsibility for implementing those constitutional protections rests with elected lawmakers — not unelected federal bureaucrats,” they said.

The group asked the ATF to answer five questions related to the matter, including what steps it plans to take to ensure that no new information that would be retained in line with the proposed rule is used to target "lawful gun owners by federal authorities or other politically-motivated purposes.”

The senators also asked what new actions the bureau plans to take to enforce the measures in Proposed Rule 2021R-08.

The letter to ATF acting Director Marvin Richardson comes amid renewed conversations around gun violence after a string of deadly mass shootings in the spring.

An April Morning Consult-Politico tracking poll found that 64 percent of registered voters said they supported "stricter gun control laws in the United States," while 28 percent said they were against tougher legislation.