US President Barack Obama appealed for public support Wednesday against a Republican plan to extend tax cuts for the richest Americans, arguing that such a move would add hundreds of billions of dollars to the national deficit.

Speaking in the working class city of Cleveland, Ohio, Obama said he would back extending Bush era tax cuts for the middle class - families with incomes below $250,000 annually or 98 percent of Americans - and not for the wealthiest two percent of households.

'Under the tax plan passed by the last administration, taxes are scheduled to go up substantially next year,' Obama said. 'I believe we ought to make the tax cuts for the middle class permanent.

'These families are the ones who saw their wages and incomes flatline over the last decade ... And because folks in the middle class are more likely to spend their tax cuts on basic necessities, this will strengthen the economy as a whole.'

Obama said that the sluggish US economy couldn't afford to spend $700 billion over the next 10 years 'to give a tax cut of about $100,000 to folks who are already millionaires', which the Republicans have called for.

The issue is expected to be high on the agenda ahead of November congressional elections, when Republicans are expected to make a strong push to oust Obama's Democrats from control of the legislature.