U.S. Democratic presidential candidate Bernie Sanders warned on Tuesday that financial-sector greed was "destroying the fabric of our nation" and said the starting point of any Wall Street reform effort is breaking up "too big to fail" banks.

"If a bank is too big to fail, it is too big to exist; when it comes to Wall Street reform, that must be our bottom line," Sanders said in a blistering speech. He said allowing banks that are too big is essentially providing them with a "free insurance policy" to make risky investments knowing the U.S. government will prevent their collapse.

The U.S. senator from Vermont — an independent and a democratic socialist popular with the Democratic Party's populist wing — gave his speech at a theater near New York's Times Square, just "a few subway stops away from the epicenter of the global financial crisis," as his campaign put it.