Barack Obama, the young Democratic senator tipped to become the first black American to occupy the White House, has revealed that he is to take the first formal step towards a presidential campaign.

Mr Obama unveiled his intentions to file a 'presidential exploratory committee' on his website today, adding that he would say more about his formal plans on February 10 in his hometown of Chicago.

"I didn't expect to find myself in this position a year ago," he said in a video posting. "I've been struck by how hungry we all are for a different kind of politics. So I spent some time thinking about how I could best advance the cause of change and progress we so desperately need.

"Our leaders in Washington seem incapable of working together in a practical, common sense way. Politics has become so bitter and partisan, so gummed up by money and influence, that we can’t tackle the big problems that demand solutions."

He said that Americans had to change their politics and come together around the common interests of the nation.

Mr Obama, 45, is the fifth Democrat in the White House race which is expected to be led by frontrunner Hillary Clinton, who has promised to make an announcement soon.

Born in Hawaii in 1961, Mr Obama is the son of a Kenyan who herded goats as a child with his father while working as a domestic servant to Kenya's British rulers.

His candidacy has created fervoured excitement among grass root democrats searching for an alternative to Mrs Clinton and his visit to the early primary state of New Hampshire last month drew sell-out crowds.

While Mr Clinton still leads the early polls, Mr Obama's star has soared rapidly.

In his statement, Mr Obama said the decisions taken in Washington over the past six years have put the country "in a precarious place."

"But challenging as they are, it’s not the magnitude of our problems that concerns me the most. It’s the smallness of our politics," he said.

Democrats who are also in the race include John Edwards, the 2005 vice-presidential nominee, Tom Vilsack, the former Iowa Governor, Dennis Kucinich, an Ohio representative and Chris Dodd, a Connecticut senator.

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