His decision, which had been widely expected, was announced on his son's Website. His son, Jesse Jackson Jr, is the Democratic representative for Illinois.

The veteran black leader said on Wednesday he could achieve more if he devotes his full attention to his campaign to pressure Wall Street into providing more start-up capital for businesses in beleaguered areas.

Jesse Jackson is still expected to be a major force in the 2000 campaign

"I've got so much work to do. I've got so many issues I want to raise. I've got so many battles left to fight," said Mr Jackson.

His decision, which had been widely expected, was announced on his son's Website. His son, Jesse Jackson Jr, is the Democratic representative for Illinois.

Mr Jackson said: "I simply believe that I can most effectively advance that work, those issues and these battles outside the context of a presidential campaign."

His decision leaves Democratic Vice President Al Gore facing a nomination challenge only from former Senator Bradley of New Jersey.

Rev Jackson has not explicitly endorsed Al Gore, but sources close to him said he planned to support the vice president.

The 57-year-old's preacher's advisers - both current and former - said part of his decision hinged around the fact that he wanted, if he ran, to win and not merely to highlight the issues of economic and social justice.

In his statement, Mr Jackson raised familiar themes.

Gore: His position has been strengthened by Rev Jackson's decision

He said: "We need people willing to give voice to the voiceless. We are, I believe, at the leading edge of the next frontier of the civil rights movement: the battle for a broader sharing of economic power and wealth.

"The people who run our companies and who control the allocation of capital in this country must come to understand the value of inclusion."

Mr Jackson has never held an elected office, but remains one of the USA's best-known black political leaders.

His first White House bid in 1984 was followed by a second populist campaign in 1988.

In both races, he was credited with increasing black voter turnout and making Democrats pay more attention to civil rights.

He heads the Chicago-based Rainbow/Push coalition which seeks to generate private-sector investment to help start businesses in poverty-stricken areas.

He is the author of two books, a TV host and President Bill Clinton's envoy for democracy in Africa.