Obama accused McCain of aiming at an extra of 300 billion-dollar tax breaks and "loopholes for big corporations and for the wealthiest Americans, and he hasn't even explained how he'd pay for it."

US Democratic presidential candidate Obama speaks at the American Israel Public Affairs Committee (AIPAC) policy conference in Washington, US, June 4, 2008. (Xinhua File Photo) 

Economy has been topping American voters' concerns and remaining a focus of debates in the 2008 presidential nomination race.

Obama's campaign said on Monday that the candidate has reached out to an economic adviser, Jason Furman, who used to help his rival, Hillary Rodham Clinton, to bolster his capability to score on the economic issue.

He also kicked off an economic tour to campaign in the states whose economy have been badly hit or threatened by the rising oil price and increasing job losses.

The Democratic candidate got a boost in winning over working-class voters on Tuesday, when the United Auto Workers International Executive Board endorsed him for believing he can rebuild the US manufacturing base and assist the auto industry.

(Xinhua News Agency June 11, 2008)