Presumptive Democratic presidential nominee Hillary Clinton could reveal her running mate as early as Friday, according to US media.

Her announcement would come ahead of the Democratic National Convention, which is due to begin on Monday in Philadelphia.

Senator Elizabeth Warren, a favourite choice among Democrats, has said she was “probably not” the choice.

Virginia Senator Tim Kaine has emerged as a leading contender for the role.

The former secretary of state may reveal her vice-presidential pick on the campaign trail in the key battleground state of Florida.