Changes to come at about 1,100 Wal-Mart stores selling guns include:
-Creating a record and alert system to record when a gun sold at Wal-Mart is later used in a crime. If the purchaser of that gun later tries to buy another gun at Wal-Mart, the system would alert the sales clerk of the prior buy and could refuse to make the sale.
-Retaining the recorded images of gun sales in case law enforcement wants to view them later as part of an investigation.
-Expanding background checks of employees who handle guns and expanding inventory controls.
Suarez said the tougher standards will come with some additional cost to the company.
"The costs are, we think, part of what it takes to be responsible. Everything is not pain-free," he said, adding that small sellers can implement many of the same rules. He did not say how long it would take to implement all the changes, but noted that software must still be created for an internal log of guns later used in crimes.
Suarez said his company may receive some pressure from gun rights groups, but added, "This is not a signal that we're getting out of firearms."
The National Rifle Association denounced the company's move.
"I view it as a public relations stunt that stigmatizes law-abiding firearms purchasers exercising their freedom under the Constitution," said NRA CEO Wayne LaPierre. He said that if politicians were serious about reducing gun crime they would worry less about legal sellers and buyers and get tougher criminal sentences for illegal gun dealers.
"I honestly think it's a corporation trying to curry favor with politicians as opposed to doing anything meaningful about stopping crime," said LaPierre.
Wal-Mart sells only rifles and shotguns in its U.S. stores, with the exception of Alaska sites, which also sell handguns.
Bloomberg urged other companies to join Wal-Mart in the initiative called the Responsible Firearms Retailer Partnership.
"We didn't pressure them, they're doing it because they think it's the responsible thing to do," he said.
Wal-Mart, the world's largest retailer, had previously tried to establish a store in New York City but failed.
The mayors' gun summit also unveiled a new lobbying effort to close what they call the "gun show loophole," which allows sales of firearms without background checks between private individuals at gun shows.
Bloomberg founded the group two years ago with Boston mayor Thomas Menino to reduce the flow of guns from store displays into the hands of criminals.
The group, largely funded by Bloomberg's personal fortune, announced it was spending more than $100,000 on television ads, starting Wednesday, featuring all three of the current main presidential candidates voicing their opposition to the gun show loophole.
The ads will run in the home states of the three candidates - John McCain of Arizona, Hillary Rodham Clinton of New York and Barack Obama of Illinois. It also will air across Pennsylvania, which holds its primary next week, as well as Florida, Maryland and Massachusetts.
The mayors group is trying to gather support in Congress to:
-End the gun show loophole.
-Require gun dealers to perform criminal background checks on all gun-handling employees.
-Close a so-called fire-sale loophole that allows gun dealers whose licenses have been revoked by the government to sell off their inventory without background checks.
-Add those placed on the terrorist no-fly list to the list of people prohibited from purchasing a firearm.
