Lawmakers grilled former Treasury Secretary Henry Paulson Thursday over the government's role in Bank of America's merger with Merrill Lynch, saying authorities withheld information about losses and intimidated bank executives into sealing the deal.

Telling lawmakers that the U.S. financial system has grown "too unstable and fragile," Treasury Secretary Timothy Geithner rolled out the Obama administration's plans Thursday for a massive overhaul of the government's financial oversight role.