The U.S. derivatives industry's front-line regulator wants retail currency dealers to face higher capital and risk-management standards after Swiss franc losses this year left a leading brokerage needing a $300 million rescue.

Dealers would have to hold more capital in trades with large customers and foreign affiliates under rules proposed Thursday by the industry-funded National Futures Association (NFA). The regulations, which are subject to approval by the Commodity Futures Trading Commission (CFTC), aim to bolster the resources of U.S.-based currency dealers when they face overseas risks.

The NFA's move comes after New York-based FXCM Inc. required a private bailout because of losses at its U.K. affiliate, which had more lenient oversight for leverage. The group "has been exploring appropriate regulatory responses designed to minimize similar losses in the future," NFA said in the proposal sent to CFTC.