Charles Taylor, the Liberian warlord-turned-president, will face the first witness at his war crimes trial today after months of costly delays that have plunged the process into financial uncertainty.

Mr Taylor, 59, the first African leader brought before an international court, has pleaded not guilty to 11 charges of crimes against humanity including murder, rape and recruiting child soldiers during the brutal civil war in neighbouring Sierra Leone. He is accused of fuelling the conflict to plunder millions of pounds of diamonds and timber.

The trial has been delayed for six months after Mr Taylor sacked his first court-appointed defence team in June and demanded extra resources. He is receiving a legal aid budget of $100,000 (£51,000) a month. Faced with such costs, the Special Court for Sierra Leone is making a fresh appeal for international donors to ensure that it can complete the trial process.

The court, which has put nine other senior figures from the 1991-2002 civil war on trial in Sierra Leone, must prepare to run well into 2010 should Mr Taylor appeal against a verdict expected in about 18 months to two years. Officials have admitted privately that, despite pledges covering most of the original cost projections, there is enough money to run only until October.

The court increased the defence budget after fears that the trial would be seen as unfair to Mr Taylor and cause fresh unrest in Liberia or Sierra Leone, where the case is being followed closely. It was moved to The Hague because of similar security concerns.

Stephen Rapp, the prosecutor, who plans to call 144 witnesses over the next ten months, said: “This is certainly the most expensive programme of legal assistance to any accused in the history of international justice.”

The prosecution is due to start with evidence from Ian Smillie, an expert on economic development and conflict diamonds. Mr Taylor is alleged to have armed, trained and controlled Sierra Leone's notorious Revolutionary United Front (RUF) rebels in exchange for blood diamonds. International investigators are trying to locate the proceeds of the plunder in order to help to pay some of the court costs and to compensate victims, many of whom had limbs hacked off.

The UN set up the court, together with the Government of Sierra Leone, on the basis of voluntary international contributions, in order to prevent the kind of cost overruns faced by tribunals for Yugoslavia and Rwanda. Elise Keppler, counsel for Human Rights Watch, said: “These trials are expensive and this is not a good way to conduct trials of serious crimes under international law. There should be a reliable, consistent source of funding.”

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