President Trump entertained the idea of breaking up big banks Monday, sending major Wall Street stocks lower.

Trump suggested that he is considering reinstating some form of Glass-Steagall, the repealed law that for decades mandated a separation between commercial and investment banks.

"There's some people that want to go back to the old system, right? So we're going to look at that," Trump said when asked about the policy by Bloomberg.

Stocks for diverse megabanks such as Goldman Sachs and Citigroup fell immediately after Trump's comments were published.

The decline came after Treasury Secretary Steven Mnuchin took credit for the administration for soaring bank stocks, telling investors to "thank me."

The Trump administration's ongoing stated support for reimposing a form of Glass-Steagall has muddied its larger message supporting easier bank regulations.

Among Republicans, however, the Trump team is relatively isolated in supporting the measure, which has little support among congressional Republicans.