His campaign for the Democratic presidential nomination will be a direct challenge to incumbent Vice-President Al Gore, favourite of the Democratic Party establishment.

"I'm more interested in leadership than polls and politics and I believe we need a new kind of leadership," Mr Bradley said in his home town of Crystal City, Missouri.

The BBC's Paul Reynolds says that Senator Bradley is now seen as a serious threat to Mr Gore, who voters see as too linked to President Bill Clinton.

Mr Bradley and Mr Gore are neck and neck in New Hampshire

The son of a banker, Bill Bradley is expected to highlight his small-town origins from where he later went on to spend 18 years in the Senate.

Democratic dual

Our correspondent says that after months of trudging round America, his campaign is suddenly being taken seriously.

Commentators continue to say that Mr Bradley's strength lies in Al Gore's weakness - a lack of charisma and the fact that he may not beat likely Republican candidate Governor George Bush.

And Mr Bradley's campaign has been boosted by a weekend vote which showed him and Al Gore running neck and neck in New Hampshire, the state which holds the first presidential primary in 2000.