* New cabinet seeks better ethnic, regional balance
* President replaces finance, foreign ministers
* Most of the old cabinet has been re-appointed (Adds detail, comments on new government)
JUBA, Aug 27 (Reuters) - South Sudan's President Salva Kiir named his first cabinet since the country declared independence last month, including former supporters of the north's main party as he set out to unite a fractured state.
Oil-producing South Sudan declared independence on July 9, after southerners overwhelmingly voted to secede from the north in a January referendum.
The buildup to its birth was marred by a wave of clashes between rival tribes and renegade militias, armed with weapons left over by decades of civil war with the north.
Kiir announced the cabinet late on Friday, naming ministers from a wider selection of areas and ethnic groups than the previous caretaker administration, said analysts.
He also named the south's new transport and interior ministers as Agnes Lokudu and Alison Manani Magaya, former members of the north's dominant National Congress Party (NCP) in the south.
Both have since left the NCP, which is led by Sudan's president Omar Hassan al-Bashir, and joined Kiir's Sudan People's Liberation Movement (SPLM).
"It is a well-balanced cabinet," said Sampson Wassara, political science professor at the south's Juba university.
He told Reuters Kiir still needed to do more to tackle corruption and strengthen state institutions.
Analysts said Kiir had included more ministers belonging to ethnic groups from the south's Equatoria states.
Africa's newest country is also one of the world's poorest and Kiir is grappling with a string of border disputes with the north and disagreements with Khartoum over oil revenues, currency and debt.
The cabinet still included many familiar faces from past administrations.
Kiir "would have found it hard to make any major changes at this stage," said Roger Middleton at Chatham House in London.
Among the new appointments listed on the government's website on Saturday, Kosti Manibe replaced David Deng Athorbei as Finance Minister and former Defence Minister Nhial Deng Nhial took over foreign affairs.
The January referendum was the climax of a 2005 peace deal that ended decades of civil war with the north.
About 2 million people died in Sudan in the conflict fought over religion, ethnicity, ideology and oil. Most follow Christian and traditional beliefs in South Sudan, while Sudan is predominantly Muslim.
South Sudan accused Khartoum this week of backing a cross-border attack by insurgents that left more than 72 people dead, the most violent incident of its kind since South Sudan gained its independence.
The United Nations pledged to support the Kiir and his new cabinet.
"This new government faces huge challenges in building Africa's newest nation. The needs of the people are great. The U.N. will have a vital role in supporting this government,' said the U.N. Secretary General's representative Hilde Johnson. (Reporting by Hereward Holland; Writing by Tom Pfeiffer; Editing by Tim Pearce)
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