* Zuma to respond by Wednesday
* ANC still split on when Zuma should go
* ANC chairman says Zuma given exit ultimatum - report
* Hopes for economy with Zuma on way out (Adds cabinet meeting delayed, Mantashe ultimatum, analyst)
JOHANNESBURG, Feb 13 (Reuters) - South Africa's ruling party ordered Jacob Zuma on Tuesday to step down as head of state after marathon talks over the fate of a leader whose scandal-plagued years in power darkened and divided Nelson Mandela's post-apartheid 'Rainbow Nation'.
Leading members of the African National Congress now want new party leader Cyril Ramaphosa to replace Zuma as president, ANC Secretary General Ace Magashule told a news conference.
But the party's national executive was split on precisely when Zuma should go, Magashule added, leaving the president's immediate fate still hanging in the balance.
The ANC did not refer directly to the scandals surrounding Zuma's presidency, but said his continued presence could "erode the renewed hope and confidence among South Africans" since the choice of new party leaders in December.
There was no word from Zuma or his spokesman, but Magashule said the president had promised to respond to the order by Wednesday. The rand weakened, with traders blaming uncertainty caused by the lack of a clear timetable.
Magashule said he had met Zuma personally to pass on the order. "We haven't given him any deadline to respond," he said. "The organisation expects him to go."
Zuma had asked the party to give him a notice period of three to six months but that had been rejected, Magashule said. "Timelines? No. The NEC believes that this is an urgent matter so it should be treated with urgency," he said.
South Africa's cabinet meeting set for Wednesday has been postponed indefinitely, the government's communication service said.
ANC chairman Gwede Mantashe told a meeting in the Eastern Cape province that the party had given Zuma an ultimatum to resign or face a motion of no-confidence, the Independent online news service reported.
"Once you resist we are going to let you be thrown out through the vote of no confidence because you disrespect the organisation and you disobey it, therefore we are going to let you be devoured by the vultures," Mantashe said in a message to Zuma, according to the Independent.
Zuma is already facing a no-confidence motion in parliament set for Feb. 22 and brought by the opposition Economic Freedom Fighters.
The ANC could throw its weight behind such a vote if it lost patience with Zuma, John Ashbourne, Africa Economist at Capital Economics said in a note. But would be a painful option for the ruling party, he added.
"Instructing MPs to vote with the opposition and against their own leader would add to splits in the party and provide an embarrassing political coup to the opposition," Ashbourne said.
Zuma's entire cabinet would have to step down if such a vote went through. He has survived several no-confidence motions in the past.
Zuma has been living on borrowed time since Ramaphosa, a union leader and lawyer once tipped as Mandela's pick to take over the reins, was elected as head of the 106-year-old ANC in December.
Ramaphosa narrowly defeated Zuma's ex-wife and preferred successor, Nkosazana Dlamini-Zuma, in the leadership vote, forcing him to tread carefully in handling Zuma for fear of deepening rifts in the party a year ahead of an election.
Despite the damning decision to order Zuma's "recall" - party speak for 'removal from office' - domestic media said the 75-year-old might yet defy the party's wishes.
Since becoming president in 2009, Zuma has been dogged by scandal. He is fighting the reinstatement of 783 counts of corruption over a 30 billion-rand (now $2.5 billion) government arms deal arranged in the late 1990s when he was deputy president.
Some within the ANC and the opposition say the Gupta family, friends of Zuma, have used their links with the president to win state contracts and influence cabinet appointments. The Guptas and Zuma have denied any wrongdoing.
South Africa's economy has stagnated during Zuma's nine-year tenure, with banks and mining companies reluctant to invest because of policy uncertainty and rampant corruption.
But since mid-November when Ramaphosa emerged as a real ANC leadership prospect, economic confidence has started to pick up. The rand - a telling barometer of Zuma's fortunes - has gained more than 15 percent against the dollar over that period.
Zuma himself engineered the ouster of former President Thabo Mbeki in 2008 shortly after taking the helm of the ANC. Mbeki was also "recalled" by the party, ending a nine-year rule marked by economic growth but marred by accusations of abuse of power that he denied. (Additional reporting by Olivia Kumwenda-Mtambo; Writing by James Macharia and Ed Cropley; Editing by Andrew Heavens)