New York City Mayor Eric Adams and other officials, including trustees of the state’s pension plans, have called on major credit card companies to create a weapon code for gun and ammunition purchases.

American Express, MasterCard, and Visa would create a four-digit merchant category code (MCC), common for other retail categories, to help them detect and report large purchases of firearms or other suspicious activity by criminals. The aim is to stop shootings before they happen.

Perpetrators of some of the worst mass shootings in the U.S., including the 2016 Pulse nightclub massacre in Florida, made questionably large weapons purchases days before committing their slaughters.

The world’s three largest credit card companies have rejected creating MCCs for guns and ammunition in the past.

Seth Eisen, a Mastercard spokesman, told The New York Post that the credit card giant is working with the International Organization on Standardization (ISO) on how to create the codes, which would appear on bank statements between Mastercard and its merchants. Mastercard wants to be sure it also protects cardholders’ privacy.

“This will help us continue to deliver a payments system that supports all legal purchases while protecting the privacy and decisions of individual cardholders,” Eisen said.

Representatives from American Express and Visa did not respond to requests from the Post for comment.

Mayor Adams said at a press conference announcing the weapon code drive that this would bring a best-practices standard to the gun and ammunitions industry:

“When it comes to guns falling into the wrong hands, we must find upstream solutions before we’re faced with downstream consequences — because downstream consequences are lost lives,” Adams said.

Queens Borough President Donovan Richards Jr, a Democrat, added: “Gun violence is a crisis that has been tearing apart too many families for far too long. The credit card companies have their role to play in this and must do their part to help combat gun violence and keep our families safe.”

Adams noted that 316 people a day are shot in the United States, with 106 dying from their injuries.