Speaking on BBC Breakfast while promoting his Seven Ages Of Britain series, the veteran broadcaster said that the TV debate format will act as a "service to the voter".
Last month, the BBC, Sky and ITV all revealed plans to stage televised debates featuring Conservative leader David Cameron, Labour Prime Minister Gordon Brown and Liberal Democrat leader Nick Clegg on the panel.
Dimbleby, who will present the BBC's programme, praised the prospect of all three leaders debating key issues on a stage for the viewing public to see.
He predicted that a hundred years from now people will view the move to US-style TV debates as a "turning point" for democracy in the UK.
Each broadcaster's 90-minute programme will be filmed in front of a selected studio audience, with ITV's version being hosted by Alastair Stewart and Sky's programme fronted by Sky News' political editor Adam Boulton.
However, it emerged earlier in the week that running the debates at peak time could lead to a scheduling clash with Champions League football.