(CNN) -- The defense in the war crimes trial of former Liberian President Charles Taylor filed an emergency motion to delay supermodel Naomi Campbell's testimony against him, the court announced Monday.
She is scheduled to take the stand against him at the Special Tribunal for Sierra Leone on Thursday.
Prosecutors say Taylor gave her a diamond during the brutal war in Sierra Leone, contradicting Taylor's testimony that he never handled the precious stones that fueled the conflict.
The defense says it hasn't seen a copy of her testimony, which interferes with Taylor's right to a fair trial. Under tribunal rules, the defense team should get advance access to prosecution witness testimony so it can prepare its arguments.
It asked the court to decide by Wednesday whether Campbell would testify Thursday, according to court papers.
Campbell did not want to be involved in the trial but was subpoenaed on July 1 to appear at the tribunal for Taylor, who faces war crimes charges over a brutal conflict in Sierra Leone that was fueled by rough diamonds, also known as blood diamonds or conflict diamonds.
Witnesses have said Taylor gave Campbell a diamond.
Prosecutors had rested their case against Taylor in February 2009. They asked to reopen it specifically to call Campbell, as well as actress Mia Farrow and a witness named Carole Taylor, court papers show.
Prosecutors said they learned in June 2009 that Taylor had given the supermodel a diamond in South Africa in 1997. Farrow confirmed it, they said.
When arguing to reopen the case, prosecutors said Campbell's testimony would prove that the former president "used rough diamonds for personal enrichment and arms purchases," according to papers filed with the U.N.-backed court.
Taylor, 62, was president of Liberia from 1997 to 2003. The war crimes charges against him stem from the widespread murder, rape and mutilation that occurred during the bloody civil war in Sierra Leone. It was fought largely by teenagers who were forced to kill, given addictive drugs to provoke violent behavior, and often instructed to rape and plunder.
Taylor is charged with five counts of crimes against humanity, including murder, sexual slavery and violence, and enslavement.
He also faces five counts of war crimes, including acts of terrorism and torture, and one count of other serious violations of international humanitarian law.
He has pleaded not guilty to the charges.
CNN's Carol Jordan contributed to this report