The International Organization for Standardization (ISO) on Friday approved creation of the merchant code following pressure from gun-control activists who say it will help track suspicious weapons purchases.

“Following ISO’s decision to establish a new merchant category code, Visa will proceed with next steps, while ensuring we protect all legal commerce on the Visa network in accordance with our long-standing rules,” Visa said in a statement.

Credit card processors use codes to identify sales by sector such as grocery stores, restaurants and more.

Gun stores have been included in a broader retail category.

The code will show where an individual spends money but not what items were purchased.

Several top US pension funds including those for government workers in New York City and California had submitted shareholder resolutions asking payment companies to weigh in on the issue.

Visa’s move to adopt the new code will pressure other payment processors like Mastercard Inc and American Express Co to follow suit.

Some gun-rights activists have worried the new code could lead to unauthorised surveillance.

Mass shootings this year, including at a Texas elementary school that killed 19 children and two teachers, have added to the long-running US debate over gun control.

US president Joe Biden has called for Congress to pass an assault weapons ban as well as US$37 billion for crime prevention programmes, with US$13 billion to hire and train an additional 100,000 police officers over the next five years.