By JEREMY W. PETERS
Published: April 15, 2008

A coalition of mayors in favor of gun control, led by Michael R. Bloomberg of New York and Thomas M. Menino of Boston, said on Monday that it had reached a 10-point agreement with Wal-Mart, the country's largest seller of guns, to track the sale of firearms more closely.

Mayor Michael R. Bloomberg attending a meeting of the coalition Mayors Against Illegal Guns in Washington on Monday.

The agreement between Wal-Mart and the group, Mayors Against Illegal Guns, which Mr. Bloomberg helped to organize in 2006, calls for turning a more watchful eye on firearm sales, including videotaping sales of guns and conducting criminal background checks on store clerks who handle guns.

It also calls for keeping a record each time the Bureau of Alcohol, Tobacco, Firearms and Explosives links a gun bought at Wal-Mart to a crime. If a person who buys a gun linked to a crime were to return to a Wal-Mart to buy another gun, the purchase would be flagged. It would then be up to the store whether to permit the purchase.

When fully put into effect, the agreement would also prohibit the sale of a gun to someone whose background check comes back with inconclusive results. In many states, people are permitted to buy firearms even if a background check comes back with inconclusive results.

"This would be good politics to get behind," Mr. Bloomberg said at a news conference in Washington with other mayors from across the country. "Hopefully it doesn't take that as a consideration to get you to do the right thing. But if nothing else, the public wants to stop the craziness of letting people who are criminals get guns."

The timing of the announcement was notable: A year ago this week, a gunman killed 32 people on the campus of Virginia Tech, and next week Pennsylvania holds its presidential primary.

The mayors also unveiled a television commercial that calls on Congress — and the three major presidential candidates — to push for a law to require background checks of people who buy guns at gun shows.

The commercial, which features video clips of Senators Hillary Rodham Clinton, Barack Obama and John McCain all expressing support for background checks at gun shows, is to begin appearing on Wednesday in Pennsylvania, as well as in the home states of the three candidates and elsewhere across the country.

As for the new guidelines at Wal-Mart, the schedule for implementation was uncertain. J. P. Suarez, the company's chief compliance officer, would not say how long it would be before the procedures were fully implemented, adding that it could be some time before parts of the plan that require new technology were in place.

"Some of the things are going to be fairly quick for us to implement," Mr. Suarez said. "Some things, because they require systems or technology inputs in our stores where we carry firearms, will take a little bit more lead time."

Paul Helmke, president of the Brady Campaign to Prevent Gun Violence, said in an interview on Monday that the program would be highly effective once it was phased in. "We do think it could make a big difference," he said. "As long as it turns from talking to actually happening around the country, it's going to be major. Hopefully it will set the standard."

As Mr. Bloomberg has tried to enhance his national image, he has focused on gun control as one of his defining issues.

His activism has earned him the ire of gun rights groups, notably the National Rifle Association.

On Monday, Wayne LaPierre, the chief executive of the association, said the effort was "more a public relations stunt than a crime fighting measure."

"What's not being done," he said, "is the prosecution of felons with guns, drug dealers with guns, gangs with guns and people illegally selling guns."