U.S. 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 Inc. and Prudential Financial Inc., and General Electric Co.'s finance arm GE Capital, 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 — the largest for any company in the financial crisis— that it has since repaid.

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

The Financial Stability Oversight Council 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. GE Capital spokesman Russell Wilkerson said the company is "reviewing the details."

Nonbank financial firms deemed "systemically important" would have to increase their cushion against losses, limit their use of borrowed money and submit to inspections by 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. If at least two-thirds of the 10 voting members agree, the council would formally put the designated firm under the central bank's supervision. Lew, the council's chairman, would have to be among the two-thirds.

AIG sold guarantees on mortgage securities that forced it to pay billions of dollars after the subprime mortgage bubble burst in 2007. AIG was intertwined with the financial system through its sale of mortgage-related investments to big Wall Street banks, which themselves eventually received bailouts.

The federal thrift agency had regulated AIG, but the company's mushrooming business involving complex investments called derivatives was run out of London and elsewhere. That business fell through the regulatory cracks.