Prosecutors today questioned the convicted former interim leader of the Sierra Leonean rebel group that Charles Taylor is accused of supporting about the friendship between the former Liberian president and the Sierra Leonean rebel group's main leader, Foday Sankoh - a friendship prosecutors say predates the invasion of Sierra Leone in March 1991.

Issa Hassan Sesay is testifying to exonerate Mr. Taylor from allegations that he (Taylor) was in control of and provided support to the Revolutionary United Front (RUF), a rebel group that waged a bloody civil war in Sierra Leone from 1991 to 2002. Today, prosecutors cross-examined Mr. Sesay, who concluded nearly three weeks of direct examination last week, about the relationship that existed between Mr. Taylor and RUF leader Mr. Sankoh. Prosecutors say that the two men became friends while they trained their respective fighters in Libya in the late 1980s and that the basis of such friendship was to provide mutual assistance to each other in their respective invasions of Liberia and Sierra Leone. When he testified as a witness in his own defense, Mr. Taylor said that he did not know Mr. Sankoh prior to the RUF's invasion of Sierra Leone in 1991. In his testimony yesterday, Mr. Sesay told the court that while they underwent training at Camp Naama in Liberia in 1990, Mr. Sankoh informed them that he was already friends with Mr. Taylor. Prosecutors today decided to dig further.

Prosecution counsel conducting Mr. Sesay's cross-examination, Nicholas Koumjian, put to Mr. Sesay that in a previous BBC interview, Mr. Taylor had announced, "It is known by everyone that I have been friendly with Foday Sankoh for many years before the revolution."

During his testimony, Mr. Taylor responded to the statement above by saying, "I said it is known by everyone that I knew Foday Sankoh before the revolution when in fact I did not."

"Was it known by all of you at Naama that Foday Sankoh was friendly with Charles Taylor or Charles Taylor was friendly with Foday Sankoh many years before the revolution?" Mr. Koumjian asked Mr. Sesay.

In response, Mr. Sesay said, "I cannot say what was happening before the revolution, but Mr. Sankoh told us at Naama that he was friends with Mr. Taylor...[He said so] at Naama and also in Sierra Leone."

Prosecutors are seeking to establish that the friendship between Mr. Taylor and Mr. Sankoh before the wars in Liberia and Sierra Leone saw the commencement of a joint criminal enterprise between the two men, and the purpose of such enterprise was to capture and control political power in their respective countries. In the pursuit of this enterprise in Sierra Leone, prosecutors allege that the RUF committed heinous crimes in Sierra Leone, crimes they say that Mr. Taylor bears the greatest responsibility for. Mr. Taylor has denied the allegations against him.

Prosecutors also pointed out that when the RUF invaded Sierra Leone in March 1991, they did so with the assistance of fighters belonging to Mr. Taylor's National Patriotic Front of Liberia (NPFL) rebel group. Mr. Sesay admitted that there were indeed NPFL fighters among the invading forces in Sierra Leone in 1991.

Mr. Sesay, however, corroborated Mr. Taylor's account that when NPFL fighters were withdrawn from Sierra Leone in 1992, Mr. Taylor did not have any contact with the RUF until in 1999 when the rebels were in peace talks with the government of Sierra Leone.

Mr. Koumjian read the testimony of a previous witness who told the court that in 1995, Mr. Taylor invited the members of the RUF external delegation to his NPFL headquarters at Gbarngha and then travelled with them to Ghana. When this was stated to Mr. Sesay, he said he did not know about it.

"Were you aware that Charles Taylor invited three members of the external delegation to spend three weeks with him in Gbarngha, and he took them to Ghana? Mr. Koumjian asked Mr. Sesay.

"No. I did not know about that because in August 1995, I was not in Sierra Leone," Mr. Sesay responded.

Mr. Koumjian also put to Mr. Sesay that he lied when he told the court in his testimony that the RUF did not give Mr. Taylor a heavy artillery weapon that was captured from Guinean soldiers fighting in Sierra Leone in 1991. Mr. Koumjian read the testimony of a previous defense witness who told the court that the RUF did give the heavy artillery weapon to Mr. Taylor in exchange for automatic rifles and materials. Mr. Sesay said he did not know about this.

Mr. Sesay's cross-examination continues on Wednesday.