* Party condemns rumours of Dos Santos' ill-health
* General election due in 2017
* Weak oil prices have hit Angola economy
* Critics accuse him of mismanaging oil wealth (Adds party official, analyst, details)
By Herculano Coroado
LUANDA, Dec 2 (Reuters) - Angolan President Jose Eduardo dos Santos, who has been in power since 1979, will not stand for re-election at national polls due to be held next year, a ruling party document showed on Friday.
Joao Lourenco, the defence minister and vice president of the ruling MPLA party, was approved by its key decision-making body as its standard bearer to succeed Dos Santos after the president proposed him a day earlier.
The party said on Thursday that rumours circulating in social media that Dos Santos was ill were untrue.
Angolans have long speculated about the president's next move since he said last March that he would stand down in 2018.
The next parliamentary election is due in 2017 and the leader of the winning party will then become president.
MPLA leader Dos Santos, a communist-trained oil engineer, was re-appointed to a new five-year term in 2012 after his party won a landslide win. After his announcement in March, it was widely assumed that he would run for re-election next year and then stand down in 2018.
"Our goal is to win the elections with qualified majority or at least with absolute majority," Dos Santos told the party's central committee at a meeting in Luanda in March.
"And the secret rests in the discipline, in the union and cohesion of everybody around our candidates in the process of the electoral campaign and in the moment of voting," he said.
Angola, a member of OPEC and currently Africa's top oil producer, has been hit hard by the slump in global crude prices. Oil export revenues account for more than 90 percent of its foreign exchange revenues.
Sub-Saharan Africa's third largest economy has held discussions with the World Bank and International Monetary Fund about possible financial assistance.
A senior party official who asked not be named said the proposal to put forward Lourenco as the party's presidential candidate was yet to be formally made public, as his selection had not yet been communicated to the MPLA's grassroots.
Analyst Luis Jimbo, director of the Angolan Institute for Electoral Systems and Democracy, said Dos Santos's decision came as a surprise.
Jimbo said the president had been expected to run as the leader of the MPLA, adding that "this was possibly a last-hour decision" by Dos Santos who felt he did not have the strength to run a campaign.
Critics accuse Dos Santos - Africa's second longest ruling leader after Equatorial Guinea's President Teodoro Obiang Nguema Mbasogo - of mismanaging Angola's oil wealth and making an elite, mainly his family and political allies, vastly rich in a country ranked amongst the world's most corrupt.
His inscrutable public demeanour belies his tight control of Angola, a former Portuguese colony where he has overseen an oil-backed economic boom and the reconstruction of infrastructure devastated by a 27-year civil war that ended in 2002. But growth has stalled sharply as oil prices fell. (Writing by James Macharia; Editing by Tom Heneghan)