Ace Magashule, secretary general of the African National Congress, said that the party had not given Mr. Zuma a deadline to respond, but added that he was certain that the president would deliver a reply the next day. “Let’s leave it to President Jacob Zuma,” Mr. Magashule said at a news conference at party headquarters in Johannesburg.
The extraordinary confrontation between Mr. Zuma and A.N.C. leaders heightened a power struggle within the party that has governed South Africa since the end of apartheid and has become less known for its heroic past than for widespread corruption and mismanagement. The power struggle has paralyzed South Africa, which has the continent’s largest economy.
In what appeared to be a turning point, the A.N.C., for the first time, moved decisively against the leader it had shielded for the past nine years against a seemingly endless series of accusations of misconduct. But in an indication of what may be the limits of the A.N.C.’s self-inquiry, party leaders stated that Mr. Zuma was being dismissed because he was harming the A.N.C.’s prospects — not because of the ethical issues surrounding him.
“President Zuma has not been found guilty by any court of law,” Mr. Magashule said. “And when we took these decisions, we did not take these decisions because Comrade Jacob Zuma has done anything wrong.”
The drawn-out negotiations over Mr. Zuma’s future have cast a pall over the optimism that followed Cyril Ramaphosa’s election in December to succeed him as leader of the A.N.C., and his pledge to steer South Africa on a new course. Although Mr. Ramaphosa, deputy president since 2014, has a mixed record in both politics and business, he has spoken forcefully against corruption and is allied with A.N.C. officials with reputations as reformers.
Party leaders did not address how they would respond if Mr. Zuma did not step down, but the A.N.C. would almost certainly have to remove him through a vote of no confidence in Parliament if he refuses to meet their demand, an option that it would like to avoid.
A no-confidence vote would bring fresh attention to the widespread corruption in the A.N.C. and expose the governing party to charges of hypocrisy. It has used its dominance in Parliament to quash eight previous opposition-led motions of no confidence, as recently as last August.
In a meeting with party leaders Monday night, Mr. Zuma was defiant, insisting that he had done nothing wrong and refusing to resign, according to the local news media.
Mr. Magashule said that Mr. Zuma had asked to serve for an additional three to six months before stepping down. But Mr. Magashule said that party leaders rejected the request, saying, “the period is too long.”
Officials pushing for Mr. Zuma’s early exit had argued that the longer he stayed in power, the harder it would be for Mr. Ramaphosa to rebuild the A.N.C. before national elections in 2019.
Mr. Magashule said that the uncertainty over the presidency would “erode the renewed hope and confidence among South Africans” since the party elections in December.
Mr. Magashule, a longtime ally of Mr. Zuma’s, dismissed suggestions that the party’s move had also been influenced by corruption charges and inquiries that the president is facing.
The A.N.C.’s decision to dismiss Mr. Zuma was the culmination of a week of high-level party meetings and direct talks that failed to resolve an impasse between Mr. Zuma and Mr. Ramaphosa. Seeking to avoid a confrontation that could deepen a party split, Mr. Ramaphosa had pressed Mr. Zuma to resign voluntarily.
Under the Constitution, Parliament selects the president, effectively putting the decision in the hands of the A.N.C.’s top leaders. Mr. Magashule said on Tuesday that the A.N.C. had no immediate plans to put forward a motion against Mr. Zuma.
A vote of no confidence was already scheduled for Feb. 22, however, and opposition parties are demanding that it be moved up to this week, putting the governing party in an awkward position. A.N.C. lawmakers would have to work with the opposition, which could then claim credit for removing the president. Or they could choose to vote against the opposition-led motion and put forward their own, prolonging the crisis.
The A.N.C.’s leaders hammered out their position in a marathon meeting of the party’s national executive committee at a hotel in Pretoria, the capital, which started Monday afternoon and lasted into Tuesday’s predawn hours.
Around midnight, Mr. Ramaphosa’s motorcade was seen making its way to Mr. Zuma’s residence, where Mr. Ramaphosa directly asked for the president’s resignation.
Mr. Magashule, who accompanied Mr. Ramaphosa, said that Mr. Zuma pleaded again for more time.
“Our discussions were very cordial,” Mr. Magashule said.
After the president refused to step down, Mr. Ramaphosa’s motorcade returned to the hotel where, in a tense meeting over the next few hours, Mr. Ramaphosa pushed members of the executive committee to formally demand that the president step down.
The developments amounted to a setback for Mr. Ramaphosa, who had confidently told South Africans increasingly weary of the continuing power struggle that Mr. Zuma’s future would be finalized during the meeting on Monday.
The situation appeared to be moving in Mr. Ramaphosa’s direction last week. A scheduled executive committee meeting was suddenly canceled after he began direct talks with Mr. Zuma, which he had optimistically described as “constructive.” But despite Mr. Ramaphosa’s reputation as a skilled negotiator, the talks ultimately proved unfruitful.
At the A.N.C. elective conference in December, Mr. Ramaphosa’s margin of victory over Mr. Zuma’s chosen successor was slim, indicating the deep party split and presaging the difficulties he would face in pressing Mr. Zuma to step down as the nation’s leader before his term expires in mid-2019.