Sudan's western region of Darfur has voted to retain its current multi-state administrative status, the electoral commission says.
More than 97% of voters in a referendum chose to remain as five states rather than form a single region, it said.
The vote was boycotted by major rebel and opposition groups which say a united region would have more autonomy.
The referendum was part of a peace process to end 13 years of conflict that has left 300,000 people dead.
Ahead of the vote, Sudanese President Omar al-Bashir, who is wanted by the International Criminal Court (ICC) on war crimes charges related to Darfur, said it would be a free and fair poll.
However, the US state department warned that the referendum could not be considered credible "under current rules and conditions".
The vote was held amid ongoing insecurity and many of Sudan's 2.5 million displaced people were not registered to vote.
The electoral commission said 3.08 million people out of 3.21 million eligible voters turned out for the referendum earlier this month.
Rebels have long sought more regional powers to end what they see as Khartoum's interference in land ownership conflicts.
They believe that the government's splitting of Darfur into three states in 1994, and then into five states, led to heavier control from Khartoum and helped to trigger the conflict that broke out in 2003.
Correspondents say the Sudanese government believes a unified Darfur would give the rebels a platform to push for independence just as South Sudan did successfully in 2011.
The ICC has indicted President Bashir on counts of genocide and war crimes committed in Darfur.
Mr Bashir - who has told the BBC he will step down as president in 2020 - has dismissed the ICC as a "political tribunal".