He and Democrats contend the nation needs the additional revenue from ending the tax cuts on the rest, while the middle class needs continued help coping with the sluggish recovery. The problem, Obama says in his campaign stump speech, is that Republican refuse to consider any kind of tax hike, even for millionaires who can easily handle it.

Republicans want to maintain the lower rates of the Bush tax cuts for everyone for a year, arguing that raising anyone's taxes in a weak economy will harm any chance for stronger recovery. They also oppose increased taxes on grounds that government needs to shrink, rather than receive more revenue that would allow it to keep growing.

Both parties say the ultimate goal is comprehensive tax reform to settle a dispute at the center of deficit reduction talks throughout the Obama presidency. However, when Senate Republicans called for an immediate vote Wednesday on each side's proposal, Majority Leader Harry Reid, D-Nevada, said no.

A Democratic leadership aide said the delay was to prolong the tax cut debate through July, but another reason may be the difficulty Reid faces in holding together his caucus to support Obama's plan.

Some Senate Democrats propose that the cutoff for extending lower tax rates should be $1 million in order to restrict higher taxes to the most wealthy, while backing the president could be difficult for those facing tough re-election battles.