Treasury Secretary Timothy Geithner unveiled the tax overhaul Wednesday, two days before a tax proposal being offered by one-time venture capitalist Mitt Romney.  He is one of the leading Republican presidential contenders seeking his party's nomination to face Mr. Obama, a Democrat, in next November's national election.

　　Government officials said the plan would cut the effective tax rate for manufacturing firms from the current 32 percent average to 25 percent.  But the proposal would raise taxes on oil and natural gas companies.  It also would require, for the first time, that U.S. companies operating overseas pay a minimum tax on their foreign earnings.

　　The top U.S. corporate rate of 35 percent is among the highest in the world, putting American firms at an economic disadvantage.  But numerous U.S. corporations, after taking allowable deductions for business expenses, often pay at a substantially lower rate, and occasionally, nothing.