US President Donald Trump has suggested he could persuade the powerful National Rifle Association lobby group to drop its strong opposition to gun restrictions after recent mass shootings reignited the gun control debate.

The NRA, one of the most powerful lobbies in the US and a frequent donor to Republican politicians, has for decades rejected gun control efforts.

It indicated in a statement on Thursday that it still opposed further gun restrictions.

But Mr Trump told reporters at the White House on Friday the NRA should have input on the issue and might come around to supporting tighter background checks on gun buyers or at least not be so strident in its opposition.

Following attacks last weekend that killed 31 people in Texas and Ohio, Mr Trump said the US needs significant background checks on gun buyers "so that sick people don't get guns".

Serious discussions are taking place between House and Senate leadership on meaningful Background Checks. I have also been speaking to the NRA, and others, so that their very strong views can be fully represented and respected. Guns should not be placed in the hands of..... — Donald J. Trump (@realDonaldTrump) August 9, 2019

He spoke to NRA chief Wayne LaPierre by phone.

"I think, in the end, Wayne and the NRA will either be there or maybe will be a little bit more neutral and that would be OK, too," Mr Trump said.

"You know, it's a slippery slope. They think you approve one thing and that leads to a lot of bad things. I don't agree with that. I think we can do meaningful, very meaningful background checks. I want to see it happen."

Mr Trump said that many attempts to restrict gun ownership have stalled in Congress in the past "but there's never been a president like President Trump.

"I have a great relationship with the NRA," he said.

Pressure from the group helped force the Republican president to back down on supporting tighter gun laws last year despite national outrage at the fatal shootings of 17 people at a high school in Parkland, Florida.

The NRA spent $US30.3 million to support Trump's 2016 presidential campaign, according to the Center for Responsive Politics, a group that tracks campaign spending.

Senate Democratic Leader Chuck Schumer, in a Twitter posting on Friday, said "it will be nearly impossible to accomplish anything meaningful to address gun violence" if Trump requires pre-approval by the NRA.

.@SenateMajLdr McConnell stated the obvious yesterday and nothing more: there will be discussions.



To get anything meaningful done to address gun violence, we need his commitment to hold a Senate vote on the House-passed background checks legislation. https://t.co/RNCqBWWJ4Y — Chuck Schumer (@SenSchumer) August 9, 2019

The Washington Post reported that LaPierre called Mr Trump this week to tell him a background check bill would not be popular with his supporters.

Mr Trump wrote on Twitter that he had "been speaking to the NRA, and others, so that their very strong views can be fully represented and respected".

As he considers whether to push for new measures, Mr Trump also has to ensure he does not lose the support of pro-gun rights conservatives as he runs for re-election next year.

Democrats are trying to galvanise public support for legislative action over what has been a contentious issue for years, even before Trump's administration. Since he became president in 2017, there have been mass shootings at a church in Texas, a concert in Las Vegas and high schools in Florida and Texas.

Mr Trump earlier this week initially appeared to support background checks but then did not mention them in a public address on Monday that focused on mental illness and media culture as possible causes of part mass shootings.

He later predicted congressional support for those background checks and blocking gun access to the mentally ill, but not for any effort to ban assault rifles.