Texas Governor Rick Perry has announced his candidacy for the Republican nomination in the 2012 presidential race.
His announcement at a South Carolina event comes as fellow candidates face their first key test of grassroots party opinion in an Iowa straw poll.
The poll is not an official primary but winning is considered a major boost.
The front-runner in national opinion polls, ex-Massachusetts Governor Mitt Romney, is not actively taking part.
Romney is expected to face a strong challenge from the conservative Mr Perry, who succeeded George W Bush as Texas governor.
The strong-jawed Perry told voters in a conference call from Columbia, South Carolina, that he wanted to take on President Barack Obama next year.
“I full-well believe I’m going to win,” he said.
In a speech to supporters, he slammed the Obama administration, saying the US “cannot afford four more years of this rudderless leadership”.
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