The national electoral council set the date one day after Nicolas Maduro, Mr. Chavez's handpicked successor, was sworn in as acting president in a ceremony largely boycotted by the opposition, which slammed it as unconstitutional.
Shortly after the date was set, the main opposition coalition announced it had unanimously chosen Henrique Capriles, who lost to Mr. Chavez in the October election, as its unity candidate again.
"We have all recognized Henrique Capriles Radonski as the person to embody this option of change," said Ramon Guillermo Aveledo, executive secretary of the Democratic Unity Roundtable (MUD).
Mr. Capriles wrote on Twitter that he was "grateful" for the offer and would announce soon whether he will accept the nomination. The Miranda state governor was picked by the MUD last year in an unprecedented primary.
Political hostilities had already begun just hours after Venezuela and more than 30 foreign leaders gave Chavez a rousing state funeral, with Mr. Maduro railing against the opposition and capitalism following his inauguration.
Emulating his late mentor's combative style, the former vice president vowed "absolute loyalty" to Chavez before donning the presidential sash, his voice cracking as he declared: "Sorry for our pain and tears; but this presidency belongs to our Comandante."
Before Maduro was sworn in, Capriles denounced the inauguration as a "constitutional fraud" and abuse of power by the government.
"Nicolas, nobody elected you president. The people didn't vote for you, kid," Capriles said.
The electoral council said candidates will be able to register on Sunday and Monday and that the campaign would be short, lasting from April 2 to April 11.
Chavez will cast a huge shadow over the election, which will almost coincide with a key anniversary in his political history.
The late leader was briefly ousted on April 11, 2002, in a coup that was organized by the chamber of commerce and the trade union with the help of some military officials. But he was restored to power by loyal soldiers on April 13 amid popular protests.
The government plans to embalm and preserve Mr. Chavez "like Lenin" to rest in a glass casket "for eternity," a move decried by the opposition, which claimed that it went against the president's wish to be buried.
Thousands of Venezuelans, meanwhile, continued to file past the open casket of the firebrand leader at a military academy, in a prolonged farewell to the man whose socialist revolution heightened class tensions in the country of 29 million.
Mr. Maduro has vowed to press on with Chavez's revolution, an oil-funded policy that has provided popular health, education and housing programs to the poor while angering the wealthy with expropriations and nationalizations.
Mr. Chavez lost his battle to cancer on Tuesday at the age of 58, leaving behind a divided country after a 14-year presidency.
He had chosen Mr. Maduro to succeed him before leaving for Cuba in December for a new round of cancer surgery, urging Venezuelans to vote for the 50-year-old former bus driver and union activist if he died.
Chavez beat Capriles by 11 points. But the 40-year-old governor gave the opposition its best result ever against the late president, garnering 44 percent, or 6.5 million, of ballots.
A recent survey by pollsters Hinterlaces gave Mr. Maduro a 14-point advantage over Mr. Capriles, though the opposition leader has questioned the firm's reliability in the past.
"The next president will have huge challenges: Earning the respect of the impoverished population, who blindly believe in Chavez, in a divided country," said Central University of Venezuela professor Agustin Blanco.
Chavez, who forged a near-mystical bond with the country's once-neglected poor, has been lying in state at the academy since Wednesday and throngs have filed past his half-open casket nonstop.
Many of his followers say they will grant their leader's wish and vote for Mr. Maduro, even though some say they still are getting to know him and that he lacks Chavez's charisma.
"Chavismo continues. It's an ideology already. Now we will not continue with Madurismo. It's Chavismo continuing through Mr. Maduro," said Omaira Salazar, 64, one of the countless people waiting in line to see Chavez.