Omar al-Bashir has resigned as commander-in-chief of the army
Sudan leader Omar al-Bashir has been officially nominated to stand for president in April's election by his northern National Congress Party (NCP).
The general election will be the first since the end of a two decade north-south civil war in 2005.
The southern SPLM party is expected to announce its candidate later this week.
The BBC's James Copnall in Khartoum says it is unlikely to be SPLM leader Salva Kiir, who is focused on his job as president of Southern Sudan.
Our correspondent says Mr Kiir will want to remain as southern leader ahead of a referendum on independence for the semi-autonomous region due in a year's time.
More than three-quarters of the population live in the north, so it is likely that a northern candidate will win the election, he says.
Mr Kiir also does not have the broad national support the late SPLM leader John Garang enjoyed, our reporter says.
Fears of violence
Earlier, Mr Bashir stepped down as commander-in-chief of the army - in accordance with electoral law - in order for his candidacy to go forward.
By James Copnall
BBC News, Khartoum
Omar al-Bashir's nomination is no surprise and with his sights set on the referendum, Southern Sudan's President Salva Kiir will almost certainly not stand. Some speculate the SPLM leader in the north, Yassir Arman, a northern Muslim, would be the SPLM's obvious choice.
It is still possible that northern opposition parties and the SPLM will field a joint candidate against President Bashir. However the parties, though grouped in a loose anti-Bashir alliance, have very different ideologies and agendas.
Among the senior northern opposition figures, the veteran Islamist Hassan al-Turabi has announced he will not run. Instead his number two, Abdallah Deng Nhial, will be the candidate of the Popular Congress Party.
Either this means Mr Turabi hopes a southern Muslim can appeal to the broadest possible constituency; or he is scared he would not score many votes himself, either through lack of popularity or rigged elections.
The nomination process comes against a backdrop of ongoing violence in the south - with repeated heavy clashes between rival ethnic groups in recent weeks.
Reports are emerging of several deaths in fresh fighting in the Gogrial region of the south's Warrap state, a region where 140 people were reported killed last week.
More than 2,000 people were killed and 250,000 people displaced in 2009 in Southern Sudan.
The 22-year war between the mainly Muslim north and the Christian and animist south claimed the lives of some 1.5 million people.
Correspondents say there is scepticism about the possibility of free or fair elections especially in areas such as the troubled western Darfur region.
However, the authorities say they are doing all they can to meet the challenge of organising what is perhaps the country's largest and most complex ballot.
The International Criminal Court issued an arrest warrant for Mr Bashir last year for alleged war crimes committed in Darfur.