WASHINGTON — The gun safety coalition that helped pressure Walmart to stop the sale of military-style ammunition and ask customers to no longer openly carry firearms in its stores is significantly expanding its campaign, NBC News has learned. The group has issued an open letter calling on U.S. companies to break financial or business ties with the National Rifle Association and to stop making political donations to NRA-backed lawmakers.

“After the recent mass shootings in Ohio and Texas, we have been reminded of the painfully high cost we all pay and the toll gun violence takes on our families, friends, communities and neighbors,” wrote leaders of the coalition that includes gun safety groups including Guns Down America, March for our Lives and MoveOn, among others.

“If Congress won’t act, it’s time that you do,” the group wrote, adding, “American employers are already doing more than Congress to keep us safe from gun violence.”

Igor Volsky, director of Guns Down America, told NBC News that with the holiday shopping season approaching, the campaign is likely to target some of the nation’s other large retailers after Walmart's actions. The coalition is choosing specific targets now before building campaigns around them in the coming weeks, he said.

The effort marks a hard pivot by activists, long frustrated by a decades-long stalemate in Congress over stricter gun laws, to press corporate America to take the lead in addressing the nation’s gun violence epidemic. U.S. gun deaths have reached their highest level in nearly 40 years, according to the U.S. Centers for Disease Control.

“We feel like conscripting American corporations in building a future with fewer guns is where the future is trending. Legislative change is going to take a long time and we need to find other avenues to move this along in the effort of saving lives,” Volsky said.

Members of Moms Demand Action and other gun control advocates hold a gun control rally at the Virginia State Capitol Building in Richmond, Va., on July 9, 2019. Michael McCoy / Reuters file

On Tuesday, GOP Congressional leaders met at the White House about the legislative agenda for fall and discussed whether it would include action on guns. Senate Majority Leader Mitch McConnell has repeatedly said he would only put legislation on the floor that President Trump would sign. Yet Trump has gone back and forth on whether he would support expanded background checks.

The Democratic-controlled House passed comprehensive background check legislation in February and the Senate shows no signs of taking it up.

In the aftermath of the shooting in an El Paso Walmart last month, the coalition came together to stage rallies, launch a petition and urge Americans to hand deliver letters to local Walmart managers asking them to end all gun and ammunition sales and break ties with the NRA.

On Sept. 3, Walmart, the nation’s largest retailer, said it would end all handgun ammunition sales and ask customers not to carry guns into stores. It will continue to sell long barrel deer rifles and shotguns and much of the ammunition for those guns. It's the latest step from Walmart to scale back the sale of weapons and ammunition, including stopping the sale of handguns everywhere but Alaska and ending sales of modern sporting rifles and starting last year.

Volsky pointed to a number of other companies that have already taken the initiative, including in the aftermath of the shooting at Marjory Stoneman Douglas High School in Parkland, Florida in 2018 that killed 17 people. First National Bank of Omaha said it would not renew a contract with the NRA to issue a branded Visa card. Enterprise Holdings Inc., the car rental company, announced it would cut off discounts for NRA members, while Allied and North American van lines, the moving service providers, terminated discounts for NRA members.

Citigroup also set restrictions on the sale of firearms by its business customers, becoming the first Wall Street bank to take such a stance.

The coalition said Walmart’s actions should accelerate corporate America’s march toward gun safety in the absence of congressional action.

“Walmart’s actions established a higher standard for corporate responsibility in the gun reform arena and we’re glad Kroger, Walgreens, Wegmans and CVS have also moved in the right direction. But we believe that every major American employer has a moral and patriotic duty to go even further.”