Venezuelan opposition leader Henrique Capriles has confirmed that he will stand in presidential elections on 14 April.
In a televised address, Mr Capriles accused the governing PSUV party of manipulating the recent death of Hugo Chavez.
Mr Chavez died on 5 March after a two-year battle against cancer.
Mr Capriles will stand against acting President Nicolas Maduro, whom Mr Chavez named as his favoured successor.
The acting president went on state television minutes after the opposition leader's appearance, accusing him of being a "fascist".
The BBC says the stage is now set for a bitter presidential campaign.