The surprise loss at JPMorgan was "a stark reminder" of how trading overseas can bring losses back to the U.S., CFTC Chairman Gary Gensler said in a statement.

JPMorgan's initial estimate of the loss was $2 billion when the bank disclosed it in May, although CEO Jamie Dimon has said the amount could grow. The New York Times, citing an internal report at the bank, said this week that the loss could reach $9 billion. The loss at the biggest U.S. bank has raised concerns about the risks large banks can still pose to the financial system just four years after the financial crisis.

Giant insurer American International Group Inc., which nearly collapsed in 2008 and received the biggest bailout of the crisis, had traded derivatives through its affiliates in London and the Cayman Islands.

The CFTC's oversight would extend to foreign banks that do substantial trading of derivatives in the U.S. However, exceptions would be made for those banks if the regulations in their home countries are considered by the CFTC to be "comparable" to U.S. rules.