The US National Rifle Association says it would oppose an outright ban on bump stock devices, like those used in the Las Vegas shooting which left 59 people dead, including the gunman.
The device is used to turn rifles into automatic weapons, capable of firing hundreds of rounds a minute.
The NRA, which has seldom embraced new firearms-control measures, stunned gun control advocates last week when it issued a statement voicing willingness to support a restriction on bump stocks.
On Sunday, the organisation said it was open to regulation but opposed any legislation banning the devices.
"We don't believe that bans have ever worked on anything. What we have said has been very clear — that if something transfers a semiautomatic to function like a fully automatic, then it ought to be regulated differently," said Chris Cox, the NRA's chief lobbyist.
Police said the gunman of the Las Vegas shooting, Stephen Paddock, 64, fitted 12 of his weapons with bump stock devices that allow semi-automatic rifles to operate as if they were fully automatic machine guns, which are otherwise outlawed in the United States.
Mr Cox and Wayne LaPierre, the NRA's chief executive, accused the Bureau of Alcohol, Tobacco, Firearms and Explosives under Democratic former president Barack Obama of paving the way for the use of bump stocks and creating legal confusion about their usage.
President Donald Trump, whose party controls both chambers of the US Congress, was an outspoken advocate of gun rights during his 2016 campaign for the White House.
The NRA spent more than $US30 million in support of his candidacy.
Several Republican politicians suggested last week that they were receptive to legislation to curb the use of bump stocks, including Kevin McCarthy, the number two Republican in the House of Representatives, who said such controls were an area where Congress may be able to act.
But House Majority Whip Steve Scalise, a Republican who himself was nearly killed by a gunman earlier this year while at a baseball practice, was cautious about potential new legislation.
"I do think it's a little bit early for people to say they know what to do to fix this problem," he said.
"A week ago most people didn't know what a bump stock was so — to think that we're now all experts and know how to write some panacea law, it's fallacy," Mr Scalise added.
Some gun control advocates praised the NRA for showing some flexibility.
"This is the first time that the gun lobby has shown willingness to come to the table and I think that's in part because Americans just simply do not accept mass shooting after mass shooting happening and Congress doing absolutely nothing," Democratic senator Chris Murphy said.
But the comments from the NRA representatives suggested nothing may have changed as they admonished calls for gun control measures in the emotional aftermath of a mass shooting.
"There used to be a common decency in this country where people paused talking about policy... they want to exploit a tragedy from day one. It's shameful, but apparently that's the new normal," Mr Cox said.
Investigators remain largely in the dark about what drove Paddock, a retired real estate investor and high-stakes gambler, to carry out the deadliest mass shooting in modern US history.