WASHINGTON - Federal regulators Friday designated MetLife Inc. for special oversight, saying the insurer is so big that its failure or other major problems would pose a threat to the U.S. financial system.

In a 9-1 vote, the Financial Stability Oversight Council - a panel of top regulators chaired by Treasury Secretary Jacob Lew - determined that MetLife was a systemically important financial institution.

The designation was created by the 2010 Dodd-Frank overhaul of financial regulations. Such firms are subject to tougher oversight by the Federal Reserve that could include requirements to hold more capital as a cushion against losses.

"After a year and a half of extensive and in-depth analysis - including significant engagement with the company - the council has determined that material financial distress at MetLife could pose a threat to U.S. financial stability," Lew said Friday. "Consistent with its mandate, the council remains focused on protecting the broader economy from the types of risk that contributed to the financial crisis."

MetLife - the largest U.S. insurer, with about $585 billion in assets in 2013 - is the fourth nonbank financial firm to receive the designation.

The panel was created by Dodd-Frank to look for emerging risks, in hopes of avoiding a repeat of the 2008 financial crisis. The council also includes Fed Chair Janet Yellen and the heads of the Securities and Exchange Commission, Federal Deposit Insurance Corp., and Consumer Financial Protection Bureau.

In 2012, the council designated Prudential Financial Inc., American International Group, and General Electric Capital Corp. as systemically important financial institutions. In 2008, the government bailed out AIG, and a special FDIC program insured as much as $139 billion in GE Capital debt.

MetLife opposed the designation and said it would consider challenging it in court. "We continue to believe that MetLife is not systemically important under the Dodd-Frank Act's criteria," the company said in a statement Thursday, "and the company has presented substantial and compelling evidence to FSOC to support this conclusion."