The party’s powerful 107-member national executive committee (NEC) met for 13 hours at a hotel outside Pretoria, and decided it would “recall” Zuma from his post, several local media outlets said.
“It took a brutal 13 hours, but the ANC’s national executive committee has decided to recall President Jacob Zuma as head of state,” the Times Live news website said, citing unnamed sources in the talks.
Other media reported that the party would write to Zuma ordering him to stand down as president, after his request for a few more months in office was rejected.
State broadcaster SABC said the ANC had given Zuma 48 hours to turn in his resignation.
ANC officials were not reachable to confirm the reports, but the party called a press conference for 12:00 pm (1000 GMT) at its headquarters in Johannesburg.
The ANC can “recall” the head of state, essentially forcing him to step down, but the process is a party-level instruction and he is under no constitutional obligation to obey.
If he refuses, he would then likely be ousted via a parliamentary vote of no-confidence within days.
As the dramatic power struggle built to a climax, African National Congress chief Cyril Ramaphosa reportedly left the all-night meeting for a face-to-face conversation with Zuma at his official Pretoria residence.
Ramaphosa’s motorcade was seen returning to the meeting at midnight. Three hours later, the talks closed.
Ramaphosa, the de-facto president-in-waiting, has been in deadlocked negotiations with Zuma, who dismissed an earlier request from party leaders to step down more than a week ago.
The stalemate around Zuma’s future plunged South Africa into political uncertainty over who is running the country, with a series of public events cancelled including last Thursday’s annual State of the Nation address to parliament.
“We know you want this matter to be finalised,” Ramaphosa, 65, told a party rally in Cape Town on Sunday to rapturous cheering.
“We know you want closure… Because our people want this matter to be finalised, the NEC will be doing precisely that.”
South African opposition parties on Monday called for early elections as the ANC’s leadership battle ground on.
“We must proceed to the dissolution of parliament… subsequent to that, we move on to an early election,” Democratic Alliance (DA) party leader Mmusi Maimane told reporters, speaking alongside several opposition parties.
The parliamentary speaker announced that an opposition request for a no-confidence vote against Zuma on Tuesday was still being considered.
Zuma’s presidency has been marred by corruption scandals, slow economic growth and record unemployment that have fuelled public anger.
He was scheduled to stand down next year after serving the maximum two terms after coming to power in 2009.
Zuma’s hold over the ANC was shaken in December when his chosen successor — his former wife Nkosazana Dlamini-Zuma — narrowly lost to Ramaphosa in a vote to be the new party leader.
The ANC has insisted there will be no delay to the budget speech, which is due on February 21.
Sunday’s rally was part of ANC celebrations marking 100 years since Nelson Mandela’s birth — as well as efforts by Ramaphosa to revive the party’s tainted reputation ahead of next year’s general election.
Zuma, 75, has not spoken publicly since February 4 when he was first asked by the party top leadership to step down.
In 2008, his supporters pushed out then-president Thabo Mbeki over allegations of abuse of power.
Under Zuma, the ANC won less than 54 percent of the vote in local elections in 2016 — its worst electoral performance since coming to power with Mandela at the helm in 1994.
Ramaphosa is a former trade unionist who led talks to end apartheid rule in the early 1990s and then became a multi-millionaire businessman before returning to politics.