JUBA, South Sudan (AP) — Former South Sudan Vice President Riek Machar has said he will run for the presidency in 2015 against President Salva Kiir who sacked him earlier this week.

Speaking publicly late Friday for the first time since he was fired, Machar said that he would contest for party's primaries and challenge Kiir.

Machar said if the country is to be united it cannot tolerate a "one man's rule or it cannot tolerate dictatorship." Tuesday's government shake-up, including the dismissal of the cabinet, followed reports of a power struggle within the ruling party especially between Kiir and Machar.

Kiir reduced the number of ministries from 29 to 18. He also suspended Pagan Amum, the secretary-general of the ruling SPLM party, pending an investigation into charges of insubordination and creating social divisions within the party.

While Kiir is leader of the ruling SPLM party, many of the dismissed ministers, including Machar and Amum, were key figures in the rebel movement that fought a decades-long war against Sudan that led to South Sudan's independence in 2011. Amum is South Sudan's chief negotiator in talks with Sudan.

Analysts expressed fear that the dismissals could lead to tribal clashes.

Machar said Kiir had the constitutional right to sack a vice president and dissolve cabinet, but criticized him for what he says is a power vacuum created after the shake-up by not replacing those who were dismissed immediately.

"I do not know why he left a vacuum. If we did not have a disciplined army we would be in a crisis. The only ruler now in the country is the president and this is not what the constitution says," Machar said.

Recently Kiir sacked the governors of South Sudan's Lakes and Unity states. But Machar said by sacking elected governors Kiir was violating the country's constitution.

Machar alleged that people who "want this country get into chaos" had advised Kiir to dismiss him, but Machar did not identify the individuals he accused. He urged the country to remain calm and united.

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The cabinet shake-up was announced on the same day South Sudan said the country would shut down its oil production by next week ahead of the deadline Sudan set for companies in its territory to stop receiving South Sudan's crude.

The stoppage — a crippling blow to South Sudan's government budget — will be the second shut-down of the country's only real industry since South Sudan peacefully broke away from Sudan in July 2011. The stoppages are evidence of the lingering bad blood between two countries.

Sudan notified South Sudan in June of its intention to stop receiving, processing and transporting South Sudan's crude within two months. Khartoum says it will only allow Juba to transport its crude through Sudanese territory if South Sudan stops supporting rebels fighting to topple the government in Khartoum.

South Sudan has repeatedly denied supporting SPLM-North rebels and in turn accuses Khartoum of supporting rebels in South Sudan led by David Yau Yau.

South Sudan derives almost all its government budget from the oil industry, but the south's oil can only be shipped to market via Sudan's pipelines.