A new proposal from President Barack Obama to limit the size and trading capabilities of big banks is sending shares of major financial institutions plummeting.

At the White House Thursday, Obama vowed to fight big banks with tougher regulations that he believes would head off the cascading failures that required billions bailout funds for Wall Street.

He wants new rules that would restrict banks in the use of depositor money and also limit how big financial institutions can become.

Shares in Citigroup Inc., JPMorgan Chase & Co., and Citigroup Inc. are all down by more than 5 percent.