JOHANNESBURG -- Amid deepening concern about the well-being of Nelson Mandela, President Jacob Zuma said Thursday that doctors had told him the former president's condition had "improved during the course of the night" and, though he was still critically ill, he was "now stable."
Mr. Mandela is "much better" than he had been late on Wednesday, Mr. Zuma said -- the latest in a series of official and unofficial assessments that have produced a degree of trepidation among South Africans and others that the former president's condition is steadily worsening.
Underscoring the gravity of the situation, Mr. Mandela's eldest daughter, Makaziwe Mandela, described his condition as "very critical" in an interview with the state broadcaster and warned, "Anything is imminent."
She added: "I won't lie. It doesn't look good."
But the statement from Mr. Zuma's office was a note of reassurance after many indications that Mr. Mandela, 94, had slid further after almost three weeks in a hospital in Pretoria, where he was initially treated for a lung infection.
The alarms began sounding late on Wednesday, when Mr. Zuma abruptly canceled a visit to neighboring Mozambique, and later visited Mr. Mandela in the hospital for the second time in 24 hours. The worries deepened as South African leaders prepared to welcome President Obama on Friday on the second leg of his African tour.
In the Soweto section of Johannesburg on Thursday, a line of television cameras stood across the street from the Mandela House Museum, where Mr. Mandela lived before his incarceration in the notorious Robben Island prison. A pair of musicians -- a young woman on bongos and a man on guitar -- played the same tune, over and over, and sang the same words again and again: "Nelson Mandela … Nelson Mandela … Nelson Mandela."
The Rev. Thami Ntongana, a Nazarene minister, said he had been asked by the local African National Congress Youth League to lead a prayer, and he was waiting for a procession from a nearby church to arrive before he began.
"My prayer will be, 'God, your will be done,' " he said. "We are sad about the situation, but we are realistic about it. We want Mandela to go in his own time, when the moment has come, and it is only God who can pull the main switch."
In another section of Soweto, called White City -- because it was one of the first sections to get electricity and so was bright white after dark -- two young men sat at a curbside with a sign reading "Pray for Madiba," a reference to Mandela's clan name, by which he is widely known in South Africa.
"All we can do is wait and see now," said Jabu Mkwele, 21, a taxi van driver when he can find work. "Madiba will go in his own time and we must be strong and let him go."
Although the effect of Mr. Mandela's illness on Mr. Obama's visit was not clear, his stay in South Africa will be overshadowed by expressions of disappointment and even anger over the American president's conduct in office.
While South African government officials promise an appropriately warm welcome, a coalition of trade union groups and left-wing political organizations is planning a "National Day of Action" on the first day of his visit, including a march on the American Embassy in Pretoria. The next day, student groups intend to protest outside the University of Johannesburg's Soweto campus, where Mr. Obama is to receive an honorary degree.
Meanwhile, two national groups, including the Muslim Lawyers Association of South Africa, have called on the South African government to arrest Mr. Obama when he lands, charging him with "war crimes, crimes against humanity and genocide" for the American drone attacks in Pakistan and elsewhere and for keeping the Guantánamo Bay prison in Cuba running.
"When President Obama was ushered into the world there was a promise for change of policy, like the closure of Guantánamo Bay, and how he is going to respond to the dispute between Israel and Palestine," Phutas Tseki, the regional chairman of the Congress of South African Trade Unions, said in announcing his group's participation in Friday's protests. "Now he is on his second term, and he continues to be arrogant and his policies continue to entrench American power to the whole globe without any change."
The scope of the protests accompanying Mr. Obama's visit, the intensity of which has surprised even some of the organizers, indicates that the country's longstanding skittishness about American foreign and trade policies has overridden its brief elation over the election of the first black president in the United States.
"The excitement that accompanied his historic 2008 election has given way to widespread cynicism on the continent," Mwangi S. Kimenyi, a senior fellow at the Brookings Institution, said in a blog post at ForeignPolicy.com.
As he walked across campus on way to yet another meeting, Masete Levy, president of the University of Johannesburg's student council, echoed that sentiment, saying that the students he represents are deeply disappointed by the gap between Mr. Obama's promises as a presidential candidate and his actual policies in office.
"There is now among the students a feeling that Obama has done nothing to the advantage of South Africa, and has only continued the American policies around the world that we thought he was going to end," he said. "He is a visitor of our government, and we do not object to that, but we do object to his being honored by our university and we want to make sure he hears our calls that he follow through on the promises he made."
For its part, the South African government says it is welcoming the protests and will not allow them to derail the president's visit.
The protests "might have a positive effect," said Clayson Monyela, a spokesman for the Ministry of International Relations. "It is a tangible demonstration of the healthy democracy we enjoy."
Alan Cowell contributed reporting from London.
This article originally appeared in The New York Times.