Election officials said the vote would not be postponed
Sudan's National Electoral Commission has said this month's national polls will not be delayed, despite a boycott threat by a major opposition party.
The Umma party's conditions for participating included a delay of four weeks for the creation of a new body to supervise the electoral commission.
A US envoy said he was confident the polls would start on time and be "as free and fair as possible".
The vote will be Sudan's first multi-party national poll since 1986.
Many parties have either already withdrawn from the elections or are threatening to withdraw.
"The electoral commission ensures that the elections will take place as envisioned, on April 11 to 13," commission official Abdullah Ahmed Abdullah said on Saturday.
The US special envoy to Sudan, Scott Gration, said members of the electoral commission had made him confident "that the elections will start on time and they would be as free and as fair as possible".
"These people have gone to great lengths to ensure that the people of Sudan will have access to polling places and that the procedures and processes will ensure transparency," he said.
Africa's biggest country
Deeply divided along religious and ethnic lines
11 April elections intended to be first multi-party national poll for 24 years
Continuing conflict in Darfur
President Bashir wanted for war crimes in Darfur
South Sudan rebuilding after 21 years of civil war
South Sudan could secede in 2011
Large oil fields near north-south border
The Umma party say it wants a new body to oversee the National Electoral Commission, which it accuses of bias in favour of President Omar al-Bashir's National Congress Party.
It also asked for "oppressive national security laws" to be frozen for the elections and demanded fair access to state media as well as caps on campaign spending.
Umma has said it will take its final decision on Tuesday, after seeing if its demands have been met.
But if the elections are not delayed there seems no way in which this major party will participate, the BBC's James Copnall reports from the capital, Khartoum.
On Wednesday, the southern Sudan People's Liberation Movement (SPLM) - which serves in a coalition at national level with President Bashir - announced it was withdrawing from the presidential election and from polls in Darfur over fraud and security fears.
The SPLM joined the unity government in 2005 as part of a peace deal ending a two-decade civil war.
A number of other parties have pulled out, including several opposition parties whose withdrawal has seriously hurt the credibility of the elections, our correspondent says.
Some 1.5 million people died in the civil war between the mainly Muslim North and the South, where most people are Christian or follow traditional beliefs.
President Bashir has threatened to cancel a referendum on independence for the south due in January if the SPLM boycotts the poll.