JUBA, South Sudan — After a tumultuous two weeks in the world’s youngest country, a new shake-up is worsening the volatile relationship between Salva Kiir, the president of South Sudan, and his longstanding opponent, R
Mr. Machar, whose bitter rivalry with Mr. Kiir helped plunge the nation into civil war soon after it declared its independence from Sudan, has been in hiding since clashes erupted in the capital, Juba, two weeks ago. He claims that he was targeted in the fighting and that his life is in danger.
Now, some members of his own fractured party have nominated a new leader to take Mr. Machar’s place. Taban Deng Gai, the minister of mining, accepted the nomination on Sunday, and a government spokesman said Mr. Kiir now recognizes Mr. Deng as the vice president.
Mr. Machar has refused to return to Juba without the deployment of more international troops to act as a buffer between the country’s opposing forces, an idea supported by the African Union and the United Nations, which already has about 12,000 peacekeeping troops stationed in the country.
“If Riek Machar comes back tomorrow, I will gladly step aside if that can bring peace for South Sudan,” Mr. Deng said. But he said he was against the deployment of international troops, as was the president, Mr. Kiir.
Supporters of Mr. Machar have cried foul, pointing out that Mr. Deng’s opposition membership had been revoked by Mr. Machar, in a statement on Friday that accused Mr. Deng of defecting to the president’s side.
Still, Mr. Deng insisted that he had the opposition’s full support because Mr. Machar was temporarily unable to serve as vice president.
“I’m just only filling a vacuum,” he said.
After more than two years of a civil war that killed tens of thousands of people, a peace deal brought the war to an end last year — at least on paper. Mr. Deng had served as Mr. Machar’s top representative during the negotiations, which started in 2014 in Ethiopia’s capital, Addis Ababa.
In April, Mr. Machar returned to South Sudan’s capital, Juba, to serve as deputy to Mr. Kiir, his wartime rival, in a transitional government. But when clashes between the two sides broke out here again on July 7, killing hundreds of people and displacing thousands more, Mr. Machar and his troops fled to a hiding spot not far from the capital.
Juba has remained largely calm since then, but the opposition has been left rudderless in Mr. Machar’s absence.
Last week, spokesmen for the opposition warned that the government was trying to install Mr. Deng as the new vice president. They added that those loyal to Mr. Machar who remained in Juba were facing threats and intimidation, including the opposition’s secretary general, Dhieu Mathok, who said he was assaulted at a hotel on July 14.
By Sunday, at an opposition ceremony to nominate Mr. Deng as the new vice president, Mr. Mathok spoke in support of the decision.
“Somebody will say, ‘It’s because he was tortured that he changed his mind,’ ” Mr. Mathok said. “That’s not true. I’m not afraid of anybody.”
Mr. Machar said government troops targeted him personally during this month’s clashes. Even now, “it seems like they are trying to kill us in the bush,” said his spokesman, Nyarji Roman, who was also in hiding.
Mr. Roman said the appointment of the new vice president would heighten tensions across the country.
“When parties sign a peace agreement, the main point is to silence the guns,” he added. “But Taban Deng has no support on the ground, and the commanders on the ground are not loyal to him. So you are putting more oil on the fire.”