PORTLAND (Reuters) - President Barack Obama accused Republican Mitt Romney on Tuesday of misrepresenting a comment he made about small business owners that the former Massachusetts governor's campaign has pounced upon as a sign the Democratic incumbent is anti-business.

Romney's campaign seized on Obama's comment that "if you own a business, you didn't build that," to portray the president as unsympathetic to small businesses that help boost the U.S. economy.

Obama's point was that successful business owners have had the public's help at some point in their lives through public education, roads or other government-funded projects that created an environment for businesses to bloom.

"It wasn't a gaffe," Romney said at a trucking company just outside of Boston last week. "It was instead his ideology."

On Tuesday Obama's campaign released an ad rejecting Romney's interpretation of the remarks, and at a campaign event in Oregon, the president addressed the issue directly.

"He's been twisting my words around to suggest that I don't value small business," Obama said of his Republican opponent.

"Now, keep in mind, in politics you have to endure a certain amount of spin. That's - everybody does it; I understand that ... Although I have to say when people omit entire sentences from a speech and they start splicing and dicing, they may have tipped a little bit over their skis. They may have gone over the edge," he said.

Obama said he had cut taxes on small businesses 18 times as president, and he defended his original comments with a list of ways that public investment had helped companies prosper.

"If you talk to any business owner, small or large, they'll tell you what also helps them succeed alongside their hard work, their initiative, their great ideas is the ability to hire workers with the right skills and the right education," he said.

"What helps them succeed is the ability to ship and sell their products on new roads and bridges and ports and wireless networks. What helps them succeed is having access to cutting- edge technology which, like the Internet, often starts with publicly funded research and development."

In a rebuttal to the Obama campaign's ad about the subject, a Romney spokesman said the president's original comment spoke for itself.

"It's clear what President Obama believes because he told us: 'if you've got a business - you didn't build that. Somebody else made that happen,'" Romney spokesman Ryan Williams said.

"He said it, and he meant it."