An alphabet soup of five federal agencies — the Fed, O.C.C., F.D.I.C., Securities and Exchange Commission and Commodity Futures Trading Commission — are coming up with the proposed changes to the rule. They won’t go so far as to eliminate the ban on proprietary trading, but they would make it easier for banks to comply and give them more control over defining what constitutes improper trading, according to three people familiar with the regulators’ plans.

In practice, the proposed changes could expand the types of trading that banks are permitted to engage in.

Banks and their regulators say the changes are needed because the 71-page rule is too complex and interferes with banks’ ability to provide market liquidity. In other words, they claim that the rule is making it much harder for banks to match buyers and sellers of financial products.

“Rather than reducing systemic risk, the Volcker Rule has impeded the efficient operation of the financial system, driving banks away from providing services valued by their customers, reducing competition in affected markets, and overall acting as a drag on the economy,” wrote Timothy Keehan, an American Banker’s Association lobbyist, in a letter last year to the Office of the Comptroller of the Currency.

Regulators appointed by Mr. Trump appear to agree. “We want banks to be able to engage in market making and provide liquidity to financial markets with less fasting and prayer about their compliance with the Volcker Rule,” Randal K. Quarles, the Federal Reserve’s vice chairman for supervision, said in a speech to bankers on March 5.