(Bloomberg) — American International Group Inc. and Prudential Financial Inc. would face new capital standards that are less stringent than those imposed on Wall Street banks under a long-awaited Federal Reserve proposal that's meant to limit the chance a major insurer could threaten the financial system.

Longer-term nature of most insurance liabilities

The Fed's plan subjects AIG and Prudential to a narrow set of categories by which they would have to measure the riskiness of their assets, the central bank said in a statement. While the proposal to be voted on Friday makes clear that the companies' will be treated in a way that's "appropriate for the longer-term nature of most insurance liabilities," the Fed didn't detail how it will determine the minimum capital the firms must maintain against their assets.

"This proposal is an important step toward capital standards that are both appropriate for our supervised insurance firms and that enhance the resiliency and stability of our financial system," Fed Chair Janet Yellen said in remarks prepared for the Friday board meeting.

The standards, which are required by the Dodd-Frank Act, apply to insurers that are deemed so big and complex that they could threaten the economy should they fail. AIG and Prudential are currently the only companies affected. MetLife Inc. successfully sued the government to avoid the designation.

Feedback accepted for 60 days

The Fed's rule-writing process is at an early stage — known as an advance notice of proposed rulemaking — that's meant to draw public comments to help the regulators craft a more formal plan. The agency will accept feedback on the capital plan for 60 days. But with a few steps still to go before the standards become a final rule, the process may be difficult to finish this year.