CME Group, the world's largest futures exchange operator, is planning to sue the Commodity Futures Trading Commission over the agency's decision to approve perpetual futures contracts.

Perpetual futures, or perps, are a type of derivatives that don't have an expiration date and allow people to bet on the price movement of assets without owning them directly.

CME CEO Terrence Duffy told CNBC on Wednesday that perpetual futures should be classified as swaps under the Dodd-Frank Act, and that this would form the basis of the lawsuit, which the company is filing on Thursday.

Last month, the CFTC approved bitcoin perpetual contracts as futures contracts. It approved Kalshi's application to make such offerings and issued a no-action stance for Coinbase Financial Markets, Inc., for its plans to offer digital commodity derivatives products.

While perps trading has grown popular in recent years, most of the action has been occurring outside of the U.S. due to regulatory ambiguity.