Donald Trump has said in private conversations that he is open to endorsing extensive background checks for gun buyers, prompting a warning from the National Rifle Association and concerns among White House aides, according to lawmakers and administration officials.

The US president, speaking to reporters before visiting Dayton, Ohio, and El Paso, Texas, where weekend shootings left 31 dead, said there “was great appetite for background checks” amid an outcry over government inaction in the face of repeated mass shootings.

Mr Trump’s previous declarations of support for tougher gun controls, including after the deadly Parkland, Florida, shooting in February 2018, have foundered without a sustained push from the president and support from the NRA or Republican lawmakers.

Even White House advisers question how far he will go on any effort.

NRA chief executive Wayne LaPierre spoke with the president on Tuesday after the president expressed support for a background check bill.

El Paso mass shooting: 20 killed at Walmart store Show all 39 1 /39 El Paso mass shooting: 20 killed at Walmart store El Paso mass shooting: 20 killed at Walmart store CCTV images of the gunman identified as Patrick Crusius The 21 year old, as he entered the Cielo Vista Walmart store in El Paso. The gunman was armed with an assault rifle and opened fire on shoppers at a packed Walmart store, killing 20. KTSM 9/AFP/Getty El Paso mass shooting: 20 killed at Walmart store Law enforcement agencies respond The Texas city’s police chief said the assault on a Walmart store on Saturday, which left another 26 people wounded, was being investigated as a potential hate crime. AFP/Getty El Paso mass shooting: 20 killed at Walmart store Shoppers exit with their hands up Shoppers exit with their hands up after a mass shooting at a Walmart in El Paso, Texas, U.S. August 3, 2019. REUTERS/Jorge Salgado NO RESALES. NO ARCHIVES. STRINGER Reuters El Paso mass shooting: 20 killed at Walmart store FBI released a picture of gunman Patrick Crusius The police officially identified the 21-year-old white male from Allen, Texas, a Dallas suburb some 650 miles east of El Paso. FBI/AP El Paso mass shooting: 20 killed at Walmart store A woman reacts after the mass shooting The attack came just minutes after a far-right manifesto appeared online. If authentic, it would make it the third mass shooting this year announced in advance on the website, which often features far-right and racist content. Reuters El Paso mass shooting: 20 killed at Walmart store Law enforcement responds to the active shooter The racist four-page document, titled “The Inconvenient Truth”, calls the Walmart attack “a response to the Hispanic invasion of Texas” and expresses support for the gunman who killed 51 people at two mosques in Christchurch, New Zealand earlier this year. AFP/Getty El Paso mass shooting: 20 killed at Walmart store A shopper hiding with an old lady behind the return and exchanges counter as the shooting began. Aaron Castaneda/Reuters El Paso mass shooting: 20 killed at Walmart store Ambulances in the car park near the scene It is ranked as the eighth-deadliest mass shooting in modern US history, after a 1984 shooting in San Ysidro, California, that claimed 21 lives. AP El Paso mass shooting: 20 killed at Walmart store Kendall Long (left) comforts Kianna Long (right) who was in the freezer section of Walmart. EPA El Paso mass shooting: 20 killed at Walmart store epa07755367 Police stand at attention after a shooting at a Walmart in El Paso, Texas, USA, 03 August 2019. According to reports, at least one person was killed and at least 18 people injured and transported to local hospitals. One suspect is in custody. EPA/IVAN PIERRE AGUIRRE IVAN PIERRE AGUIRRE EPA El Paso mass shooting: 20 killed at Walmart store Shoppers exit with their hands up. Reuters El Paso mass shooting: 20 killed at Walmart store Shopping carts sit next to a curb after the shooting. EPA El Paso mass shooting: 20 killed at Walmart store El Paso Fire Medical personnel arrive at the scene. AP El Paso mass shooting: 20 killed at Walmart store Walmart employees react after. AP El Paso mass shooting: 20 killed at Walmart store A woman runs to police near the scene. AP El Paso mass shooting: 20 killed at Walmart store Several law enforcement agencies respond. AP El Paso mass shooting: 20 killed at Walmart store People arrive at MacArthur Elementary looking for family and friends as the school is being used a re-unification centre. AP El Paso mass shooting: 20 killed at Walmart store Residents Erica Rios, 36, and Alma Rios, 61, cry outside a reunification centre. AFP/Getty El Paso mass shooting: 20 killed at Walmart store People gather in Juarez, Mexico, in a vigil for the Mexican nationals who were killed. AP El Paso mass shooting: 20 killed at Walmart store A child takes part in a vigil in Ciudad Juarez AFP/Getty El Paso mass shooting: 20 killed at Walmart store Francisco Castaneda joins mourners taking part in a vigil at El Paso High School. Reuters El Paso mass shooting: 20 killed at Walmart store Presidential candidate and former congressman Beto O'Rourke, right, meets with mass shooting survivor, Rosemary, at University Medical Centre Beto O'Rourke Facebook via AP El Paso mass shooting: 20 killed at Walmart store From left, Melody Stout, Hannah Payan, Aaliyah Alba, Sherie Gramlich and Laura Barrios comfort each other during a vigil for victims of the shooting. AP El Paso mass shooting: 20 killed at Walmart store A sign is posted near the scene Getty Images El Paso mass shooting: 20 killed at Walmart store Police cars parked below the Walmart sign block a road outside while investigating. EPA El Paso mass shooting: 20 killed at Walmart store Sherie Gramlich reacts during a vigil. AP El Paso mass shooting: 20 killed at Walmart store A man places flowers at the site Reuters El Paso mass shooting: 20 killed at Walmart store People take part in a rally against hate a day after a mass shooting at the Walmart store Reuters El Paso mass shooting: 20 killed at Walmart store Lupe Lopez holds a picture of a victim during a vigil for victims AP El Paso mass shooting: 20 killed at Walmart store People take part in a rally against hate a day after a mass shooting at a Walmart store, in El Paso, Texas, U.S. August 4, 2019. REUTERS/Jose Luis Gonzalez JOSE LUIS GONZALEZ REUTERS El Paso mass shooting: 20 killed at Walmart store Elsa Mendoza Marquez, a Mexican schoolteacher who was married and the mother of two adult children, was one of the victims Getty El Paso mass shooting: 20 killed at Walmart store People with the Mexican flag and the US flag take part in a rally against hate a day Reuters El Paso mass shooting: 20 killed at Walmart store People raise their arms in the air during a vigil for victims AP El Paso mass shooting: 20 killed at Walmart store People react and embrace each other Getty El Paso mass shooting: 20 killed at Walmart store Women light candles at a make shift memorial at the site of a mass shooting EPA El Paso mass shooting: 20 killed at Walmart store Adria Gonzalez (centre) who is being hailed as a hero for leading some Walmart customers to safety, speaks to the crowd AFP/Getty El Paso mass shooting: 20 killed at Walmart store People hold up their phones AFP/Getty Images El Paso mass shooting: 20 killed at Walmart store Beto O'Rourke speaks to the crowd AFP El Paso mass shooting: 20 killed at Walmart store People react during a prayer and candle vigil organized by the city, after a shooting left 20 people dead at the Cielo Vista Mall WalMart in El Paso, Texas, on August 4, 2019. - A shooting at a Walmart store in Texas left multiple people dead. At least one suspect was taken into custody after the shooting in the border city of El Paso, triggering fear and panic among weekend shoppers as well as widespread condemnation. It was the second fatal shooting in less than a week at a Walmart store in the US and comes after a mass shooting in California last weekend. (Photo by Mark RALSTON / AFP)MARK RALSTON/AFP/Getty Images MARK RALSTON AFP/Getty

Officials said Mr LaPierre told him the move would not be popular among Mr Trump’s supporters and argued against the bill’s merits.

The NRA declined to comment.

Advisers to Senate majority leader Mitch McConnell said he would not bring any gun-control legislation to the floor without widespread Republican support.

Mr Trump has hesitated, current and past White House officials said, between wanting to do more and growing concerned that doing so could prompt a revolt from his political base.

Even some supporters of the Manchin-Toomey bill, which would expand background checks to nearly all firearm sales, have said it is unlikely to pass.

“I don’t think the president or his Republican allies are going to become out of nowhere advocates of aggressive gun control,” said Matt Schlapp, who leads the American Conservative Union and is a close ally to MrTrump.

Mr Trump has focused on guns extensively since the shootings, calling lawmakers and surveying aides about what he should do – outreach that began on Sunday evening.

The president also asked lawyers about what he could enact through an executive order, officials said.

“He seems determined to do something and believes there is space to get something done this time around,” said Senate Judiciary Committee chairman Lindsey Graham, who said he had spoken to Mr Trump “four or five times” since the shooting. “The president has a pretty common-sense point of view. He’s never been a sports or gun enthusiast. But he is more determined than ever to do something on his watch.”

Mr Manchin said Mr Trump called him at 6.30am Monday and that the two spoke again on Tuesday, when Mr Trump said he wanted legislation before September and asked questions about the Manchin-Toomey bill.

He said he told the president that he would need to back any gun-control legislation or it would fail again.

On Tuesday, Mr Trump outlined some NRA concerns in a second call with Mr Manchin. “We talked about that,” the senator said. “I told him, we don’t expect the NRA to be supportive. Mr President, in all honesty, when you did the bump stocks, they weren’t for you. They were against that, too. You didn’t take any hit on that.”

In March, the Justice Department administratively banned bump stocks, the devices used to make semiautomatic rifles fire rapidly like machine guns.

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Some measures – such as a ban on assault weapons – have been ruled out, White House officials and legislative aides say.

Recent polls indicate a majority of Americans support some form of a ban on assault rifles, though there is a large partisan divide and fewer than half of Republicans support such measures. A July NPR-PBS NewsHour-Marist poll found 57 per cent of the public supported a ban on “the sale of semiautomatic assault guns, such as the AK-47 or the AR-15". Fewer than three in 10 Republicans supported the proposal, rising to a slight majority of independents and more than eight in 10 Democrats.

“There’s no political space for that,” Mr Graham said. “So I don’t think he’s going to go down that road.”

However, about nine in 10 Americans support requiring background checks for all gun purchases, including more than 8 in 10 Republicans, Democrats and independents, according to polling.