LONDON ? British supermodel Naomi Campbell will give evidence at the war crimes trial of former Liberian president Charles Taylor about a "blood diamond" he allegedly gave her, her spokeswoman said Friday.

"Naomi Campbell has confirmed she will attend the Charles Taylor trial at The Hague as per the court's request. She is a witness who has been asked to help clarify events in 1997," her spokeswoman said.

The war crimes court ordered Campbell last week to testify on July 29 about a diamond she was allegedly given by Taylor after a celebrity dinner hosted by then South African president Nelson Mandela in September 1997.

Taylor has been on trial since 2008 for his alleged role in the civil war in Sierra Leone, accused of arming rebels in return for illegally mined diamonds.

"Miss Campbell has made it clear that she is willing to help the due process of law," said the spokeswoman from The Outside Organisation PR firm.

"For avoidance of doubt she is not being accused of any wrongdoing and is not on trial."

Campbell will have to testify about claims by her former agent Carole White and actress Mia Farrow that she was given the diamond.

The prosecution alleges the gem was among those Taylor had obtained from Sierra Leone rebels and took to South Africa "to sell... or exchange them from weapons."

It believes Campbell's evidence will be direct evidence of Taylor's possession of rough diamonds, a claim he has denied.

When it ordered the model to appear, the Special Court for Sierra Leone warned she could face up to seven years in jail if she failed to turn up.

Campbell had previously refused to talk to prosecutors about the alleged gift.

The court "hereby orders you to appear as a witness in the case of Prosecutor v Charles Ghankay Taylor on Thursday July 29, 2010 at 9:00 a.m. (0700 GMT) or to show good cause why you cannot comply with this subpoena," states the subpoena addressed to the model.

The court said there was "at least a good chance that the information provided by Ms Campbell would be of material assistance" in the case.

Taylor, 62, is charged with 11 counts of war crimes and crimes against humanity stemming from the 1991-2001 civil war in neighbouring Sierra Leone, where he is alleged to have armed Revolutionary United Front (RUF) rebels in exchange for rough diamonds.

He has pleaded not guilty to charges of murder, rape, conscripting child soldiers, enslavement and pillaging.

The RUF is blamed for the mutilation of thousands of civilians who had their hands and arms severed in one of the most brutal wars in modern history, which claimed some 120,000 lives.