Wall Street banks may be close to winning one of their biggest lobbying fights this year by beating back U.S. requirements that would have led to billions of dollars of additional costs on derivatives trading.

The Commodity Futures Trading Commission (CFTC) is considering a parallel version of a rule approved by banking regulators last month that governs how much collateral must be posted between divisions of the same bank, according to people with knowledge of the matter who asked not be identified because the rule isn't public yet. The banking regulators softened the requirements from an earlier proposal, leaving Wall Street looking to the CFTC to endorse that move.

The CFTC's current draft, which could still change before a final vote slated for next month, wouldn't require that a swap-dealer division collect collateral from an affiliated unit such as a U.S.-insured bank, the people said. That shift would cement the industry's win last month when the Federal Reserve, Federal Deposit Insurance Corp. (FDIC), and other regulators said U.S.-insured banks don't have to post collateral to their affiliates.