A key northern opposition¹ party in Sudan has issued an ultimatum² to President Omar al-Bashir to ensure free and fair elections this month.

苏丹北方一个主要反对党向总统奥马尔·巴希尔发出最后通牒：必须确保本月选举自由、公平地进行。

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If Sadiq al-Mahdi's party boycotts the polls, the vote will be discredited⁵

Ex-Prime Minister Sadiq al-Mahdi's Umma party says if its terms are not met by Tuesday it will boycott³（联合抵制，拒绝参加） presidential, parliamentary and state polls.

Its eight conditions include a delay of four weeks for a new body to supervise（监督，管理） the election commission to be set up.

Most major parties have already withdrawn⁶ from the presidential race.

President Bashir, who is wanted for alleged⁷ war crimes in Darfur, has frequently rejected the idea of delaying Sudan's first multi-party national poll in 24 years.

The BBC's James Copnall in the capital, Khartoum, says the Umma party's eventual⁸ decision is likely to influence what several other northern opposition parties do.

Some parties have already said they will boycott the 11-13 April elections completely, while others are unsure.

Our reporter says if the main northern opposition do drop out（退出，脱离） , the credibility of the elections will be damaged hugely.

Crisis talks

The Umma ultimatum came after Mr Mahdi had met with the US special envoy⁹ to Sudan, Scott Gration.

Mr Gration had said earlier that if the main opposition withdrew from the legislative¹⁰ elections it was not clear whether they would still be held.

The Umma party say it wants a new body to oversee¹¹（监督，审查） the National Electoral Commission, which it accuses of bias¹²（偏见） in favour of Mr 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.

On Wednesday, the southern Sudan People's Liberation Movement (SPLM) - which serves in a coalition¹³ 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 one party not to be worried by the political climate is the Popular Congress Party of veteran Islamist Hassan al-Turabi, who has said the PCP will take part in the polls.

In a statement, the Umma party leader also said the referendum（公民投票） on independence for the south should not be used as a political tool.

President Bashir has threatened to cancel the January vote if the SPLM boycotts the poll.

The SPLM joined the unity¹⁴ government in 2005 as part of a peace deal ending a two-decade civil war.

Some 1.5 million people died in the conflict between the mainly Muslim North and the South, where most people are Christian¹⁵ or follow traditional beliefs.