However, Austan Goolsbee, a key economic official in the Illinois senator's inner circle, told Reuters that he believed Obama does want oil and gas companies and private equity firms to pay higher taxes.
"As an overall matter do corporate rates need to go up? No," Goolsbee said in an interview on Thursday.
"There are many corporations for whom he does think they need to go up," Goolsbee added. "When he says we need to close all the loopholes for the oil and gas industry, he is saying their corporate taxes need to go up. They're not paying their fair share."
As Obama takes a commanding lead over New York Senator Hillary Clinton in the race for the Democratic nomination, investors are hungry for a clearer picture of how the first-term senator would alter US financial policies if he wins the White House.
Goolsbee, an economics professor at the University of Chicago Graduate School of Business, sketched out Obama's positions and sought to assuage concerns on Wall Street that he would be less open to global trade than President Bush.
"I don't think he views himself as a protectionist," Goolsbee said. He said Obama favoured expanding access to global markets through trade deals such as the World Trade Organisation's Doha round so long as labour and environmental standards were in place.
Obama has won labour support for his criticisms of the North American Free Trade Agreement (Nafta) which he says he wants to amend.
Goolsbee criticised the Bush administration for not enforcing existing trade agreements and bringing too few cases before for the WTO.
The senator is also "very concerned" about the country's current account deficit with China and other nations.
Obama supports trade deals