WASHINGTON — Federal regulators have proposed that a group of firms that aren’t banks be deemed potential threats to the financial system that need stricter government oversight.

Big insurers American International Group and Prudential Financial said they are among the firms. The near-collapse of AIG in 2008 helped trigger the financial crisis and it received a $182 billion federal bailout that it has since repaid.

The Financial Stability Oversight Council on Monday didn’t name the nonbank financial firms because they have 30 days to notify the council that they’re contesting the proposed designation. The council didn’t say how many firms it wants to designate as so big and interconnected that their potential troubles could imperil the financial system.

In its statement, AIG didn’t say whether it intended to challenge the designation. Prudential said it is considering whether to request a hearing before the council to contest it.

Nonbank financial firms include insurers, hedge funds, mutual fund companies and private equity firms.

Those deemed “systemically important” would have to increase their cushion against losses, limit their use of borrowed money and submit to inspections by Fed examiners.

The regulators’ council, which includes Treasury Secretary Jacob Lew and Federal Reserve Chairman Ben Bernanke, took the action in a closed meeting. It was the most significant step yet by the council, which was created by the financial overhaul law to help prevent another financial meltdown.

The council will have to vote again to finalize each designation.