WASHINGTON—Big U.S. insurers Prudential Financial Inc. and American International Group Inc. would face tougher capital requirements than their peers under new rules outlined for the first time Friday by the Federal Reserve’s point-man on regulation.

Fed governor Daniel Tarullo said the Fed will propose rules “in the coming weeks” that will have higher compliance costs for insurers considered “systemically important” to the U.S. financial system.

That group currently includes AIG and Prudential, but not MetLife Inc., which won a court case overturning its systemic label earlier this year. The government has appealed MetLife’s win.

The Fed gained authority for the first time to regulate insurance companies under the 2010 Dodd Frank law, but has taken more than five years to propose rules for the industry. Mr. Tarullo’s remarks Friday were the central banks most detailed description to date of the pending regulations.

Mr. Tarullo didn’t give all the details of the Fed rules, but he sketched them out in a speech to the National Association of Insurance Commissioners, a group of state regulators. He said the Fed will propose different rules for systemic insurers than for other insurance companies it regulates.
The central bank also regulates a dozen U.S. insurance companies that own banks, including Nationwide Mutual Insurance Co. and State Farm Mutual Automobile Insurance Co.