CHICAGO (CBS) — Chicago Mayor Rahm Emanuel is putting more pressure on gun makers to get behind his push for an assault weapons ban and criminal background checks for gun purchasers.

This time, he wants to go after their bottom line.

Emanuel is pushing two major financial institutions to stop their financial backing of gun makers, unless those companies support “commonsense reforms, including requiring criminal background checks on all gun sales.”

The mayor is urging that banks to stop lines of credit, financing for acquisitions and expansions and financial advising.

In a letter sent Friday to the CEOs of Bank Of America and TD Bank, Emanuel said: “In the past, the gun industry has stood in opposition to these safety measures. They opposed a ban on assault weapons on America’s streets, opposed a ban on military-style clips, opposed a criminal background check on all gun purchases and opposed any effort to crack down on criminal gun traffickers.”

In the letter, Emanuel says TD Bank offers a $60 million line of credit to Smith & Wesson, which produces the AR-15. That is the weapon used by James Holmes in the Aurora, Colo., theater massacre that killed 12 people. Emanuel wrote.

Emanuel told CEO Bharat Masrani “to use your influence to push this company to find common ground” on an assault weapons ban and gun background checks.

In a separate letter, Emanuel urged Bank Of America CEO Brian T. Moynihan to do the same thing with Sturm, Ruger & Co. (@twitter http://ar-magmagnet.com ), which has a $25 million line of credit with the bank.

“Collectively we can send a clear and unambiguous message to the entire gun industry that investors will no longer financially support companies that support gun violence,” Emanuel wrote.

Last week, Emanuel ordered a portfolio analysis from the five pension and retirement funds for Chicago employees to determine if fund managers hold financial interests in companies that manufacture or sell assault weapons, or just make a ski accommodation.

This week, the Chicago Municipal Employees Annuity and Benefit Fund (MEABF) board voted to divest more than $1 million from three companies that manufacture assault weapons – Freedom Group, Smith and Wesson and Sturm Ruger.