WASHINGTON (AP) — Former Federal Reserve Chairman Paul Volcker is defending a federal rule bearing his name that would prohibit banks from trading for their own profit.

Volcker says in a letter supporting the rule that commercial banks backed by government deposit insurance shouldn't be able to engage in speculative trading.

"Proprietary trading is not an essential commercial bank service that justifies taxpayer support," he wrote.

Wall Street executives have opposed the so–called Volcker rule. They say it would limit trading on behalf of customers and put them at a disadvantage with non–U.S. banks, which aren't subject to the ban.

Congress directed regulators to draft the rule under the 2010 financial overhaul. It was a response to bets banks placed on mortgage–backed securities, which hastened the financial crisis and led to taxpayer–funded bailouts.