OAKLAND -- President Obama accused rival Mitt Romney of "knowingly twisting” his comments about American business, in what amounted to his most forceful response to more than a week of sustained attacks by Republicans over a sound bite the president’s campaign argued was taken out of context.

In remarks to a feisty audience at Oakland’s Fox Theater on Monday evening, Obama contended that Romney had misrepresented what he said this month when he spoke of the role government plays in supporting the growth of business. He said Romney's response showed he fails to appreciate the best way to grow the economy in a balanced way.

At issue were the president’s remarks at a campaign stop in Roanoke, Va., on July 13, where he spoke of his belief that many wealthier Americans were willing to "give something back” to help grow the U.S. economy.

"If you've been successful, you didn't get there on your own,” Obama said at the time. "If you were successful, somebody along the line gave you some help. There was a great teacher somewhere in your life. Somebody helped to create this unbelievable American system that we have that allowed you to thrive. Somebody invested in roads and bridges. If you've got a business, you didn't build that. Somebody else made that happen.”

Republicans portrayed a truncated version of that argument -- that "if you’ve got a business, you didn’t build that” -- as showing that Obama was hostile to American business.

Obama raised the flap Monday while warning his supporters that Republicans would spend unprecedented sums distorting his vision this fall.

"Earlier today Gov. Romney was at it again, knowingly twisting my words around to suggest that I don’t value small businesses,” he said, referring to his opponent's comments at a campaign event in Southern California that morning. "In politics we all tolerate a certain amount of spin. I understand these are the games that get played in political campaigns. But when folks omit entire sentences of what I said -- they start splicing and dicing -- you may have gone a little over the edge.”

Obama said he believed "with all my heart that it is the drive and the ingenuity of Americans who start businesses that lead to their success.”

"I always have, and I always will,” he emphasized.

Obama said business owners understand that to succeed, they need a well-educated workforce, research and development that’s often funded by government, and a healthy middle class to purchase their goods.