A presidential election to appoint a successor to Hugo Chavez is to be held in Venezuela on 14 April.
It is expected that opposition leader Henrique Capriles, who lost to Mr Chavez in a vote last October, will contest the election.
The announcement follows the appointment of Mr Chavez's favoured successor, Nicolas Maduro, as acting president.
The pair have until Monday to register their candidacy for the vote.
Mr Chavez died on Tuesday at age 58 after a two-year battle with cancer.
Mr Maduro, a former bus driver and union leader turned politician, is seen winning the election comfortably, according to two recent polls.
The former vice president pushed a snap election to benefit from a wave of empathy triggered by Mr Chavez's death, and was sworn in as acting president on Friday to the fury of Mr Capriles.
The 40-year-old Miranda state governor, who lost to Mr Chavez in October but garnered the oppositions' biggest vote against him, accused the government and Supreme Court of fraud for letting Maduro campaign without stepping down.
Mr Capriles says, if elected, he would copy Brazil's "modern left" model of economic and social policies.
Venezuela's opposition coalition backed Mr Capriles as its candidate, and he is widely expected to formally accept the nomination.