Omar al-Bashir is favourite to win re-election as president
Sudan's President Omar al-Bashir has warned that any delay to April elections could affect next January's referendum on secession for the south.
His comments come amid rumours that the former southern rebels, the SPLM, will call for a delay of the elections - the first national vote in 24 years.
Other northern opposition parties have already called for a delay, saying the polls will not be free and fair.
The referendum was part of a 2005 deal ending a 21-year north-south civil war.
The conflict between the mainly Muslim north and the Christian and animist south claimed the lives of some 1.5 million people.
Correspondents say the idea of secession is popular in the south - and while Mr Bashir's party would prefer the country to remain united, the president has said he would honour the outcome of the referendum.
Ballot paper concerns
On Monday, the Sudan People's Liberation Movement's deputy secretary general in the south said the party did not want a delay if a free vote could be guaranteed by the election commission.
But Anne Ito said there were concerns that ballot papers for April's parliamentary and presidential elections were being printed on government printing presses.
The BBC's James Copnall in Khartoum says the northern opposition parties and the SPLM are due to meet on Wednesday to discuss a common position.
A meeting between Mr Bashir and SPLM leader Salva Kiir - who is also president of the south - to discuss the crisis was called off on Tuesday.
Last week, Mr Bashir threatened to expel foreign election monitors after they suggested the elections should be delayed.
Our correspondent says President Bashir needs an electoral victory to give him credibility.
Violence between rival ethnic group continues to claim hundreds of lives each year in the south, making it difficult to ensure security during the election.
In Darfur, hundreds of thousands of people still live in refugee camps after a separate conflict.