South Sudan is counting down the hours until it becomes the world's newest nation on Saturday 9 July.
Sudan's President Omar al-Bashir and dignitaries from around the world will be attending the celebrations in the southern capital, Juba.
Sudan has announced its official recognition of its new neighbour - the first country to do so.
South Sudan's independence follows decades of conflict with the north, in which some 1.5 million people died.
Under the 2005 peace deal, a referendum was held on independence, which was favoured by more than 99% of voters.
The new country will be rich in oil, but it will be one of the least developed countries in the world following the long conflict.
The celebrations will begin after midnight local time (2100 GMT) around the countdown clock in the centre of Juba.
The BBC's Will Ross in the town says in the lead-up to the historic event, radio stations have been blaring out South Sudan's new anthem.
"The Republic of Sudan announces that it recognises the Republic of South Sudan as an independent state, according to the borders existing on 1 January 1 1956," Minister of Presidential Affairs Bakri Hassan Saleh said in a statement broadcast on state television.
Earlier this week, President Bashir pledged his support to South Sudan and said he wanted the new country to be "secure and stable".
"We will bless our brothers in the south over their country and we wish them success," said Mr Bashir, who agreed the 2005 peace deal with the Sudan People's Liberation Army (SPLA).
But he warned that "brotherly relations" depended on secure borders and non-interference in each others' affairs.
There had been fears that war could resume after recent fighting in two border areas, Abyei and South Kordofan, which has forced some 170,000 people from their homes.
But separate deals in recent weeks, and the withdrawal of rival forces from the border, have calmed tensions.
The UN Security Council has passed a resolution approving a new 7,000-strong peacekeeping force for South Sudan - but this is basically a rebranding of the force which was already in Sudan, mostly in the south.
The government in Khartoum has said their mandate would not be renewed, leading the US to argue that the 1,000 UN troops should be allowed to remain in South Kordofan.
The 1,000 troops in the disputed town of Abyei are to be replaced by 4,200 Ethiopian soldiers.
Rebecca Garang, the wife of the late John Garang who led the southern rebels in the civil war, told the BBC her people had no quarrel with the people of the north, only with their government.
"There are many colleagues and comrades who perished during the war but we are here for their blood," she said.
"So we are very happy and grateful for their contribution for this nation."
Our correspondent says keeping both the predominately Muslim north and the south stable long after the celebratory parties have ended will be a mighty challenge.
The two sides must still decide on issues such as drawing up the new border and how to divide Sudan's debts and oil wealth.
Analysts say the priority for Khartoum will be to negotiate a favourable deal on oil revenue, as most oilfields lie in the south.
At present, the revenues are being shared equally.
Khartoum has some leverage, as most of the oil pipelines flow north to Port Sudan on the Red Sea.
Citizenship is also a key issue which has not yet been decided.
According to the state-run Sudan Radio, the citizenship of South Sudanese living in the north has now been revoked.
Earlier this week, thousands of southern Sudanese civil servants working in the north had to leave their jobs ahead of the split.