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.

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.