Republican Donald Trump has said he would like people on terror watch lists to be prevented from buying guns, in the wake of the Orlando shootings.
The presumptive presidential nominee tweeted that he would meet the National Rifle Association (NRA) to discuss the issue.
The NRA responded by saying it would meet him but it already opposes terrorists from buying guns.
Forty-nine people were killed in a gay nightclub by Omar Mateen, who had been put on a terror watch list by the FBI.
His wife is also being questioned in connection with the atrocity, the worst mass shooting in modern US history.
Up to now, Mr Trump has been a strong supporter of protecting gun rights and his candidacy was endorsed by the NRA, a powerful gun lobby, last month.
But on Wednesday, he tweeted: "I will be meeting with the NRA, who has endorsed me, about not allowing people on the terrorist watch list, or the no fly list, to buy guns."
Mr Trump made a similar point in a television interview last November but had not mentioned it since the recent attacks.
The FBI has two terror "watch lists". The smaller one bans flying to and from the US and there is also a larger one, which Mateen was on.
Mateen was put on that list for 10 months while under investigation following inflammatory comments at work.
But the FBI concluded there was no evidence he was a terror threat.
The 29-year-old, a US national with Afghan parents, bought an assault rifle and a handgun in early June.
An NRA statement said its position had not changed.
"Anyone on a terror watchlist who tries to buy a gun should be thoroughly investigated by the FBI and the sale delayed while the investigation is ongoing."