WASHINGTON - Sen. Tom Harkin wants to create a new tax, but he says it's just an itty-bitty one - fractions of a penny on the dollar.

Still, it would collect big money from federal taxpayers: $350 billion over 10 years.

The Iowa Democrat and other lawmakers announced Thursday that they're making a fresh run at a transaction tax on Wall Street trades. For every $100 in trades, the tax would be three cents.

"There's no question that Wall Street can easily bear this modest tax," Harkin said at a Capitol Hill press conference. "I predict that once it's in place, few will even notice it."

The tax would not apply to new issuances of stocks or bonds, but it would apply to traded stocks and bonds, as well as options, puts and many other complex financial instruments.

The idea has been floated before without gaining traction. Top members of the Obama administration rejected it.