The Special Criminal Court heard today that the 1998 bomb attack on Omagh, Co Tyrone, was carried out jointly by the "Real IRA" and the Continuity IRA.
Prosecuting lawyers at the preliminary hearing told the court Mr Michael McKevitt (51) from Dundalk, Co Louth, told a meeting that the Omagh bomb was fused by the "Real IRA" but that the target had been selected by the Continuity IRA.
The account of the meeting came from Mr David Rupert, a US citizen who infiltrated the "Real IRA" for British Intelligence and the FBI.
Mr McKevitt - suspected of being the leader of the "Real IRA" - is the first man to be charged in the Republic with directing terrorism. He is also charged with being a member of an illegal organisation.
Mr McKevitt talked of the bombing at a series of meetings he had with Mr Rupert, set to be the main witness for the prosecution in his trial, which begins next February.
At another of the meetings Mr McKevitt was alleged by prosecuting counsel Mr George Birmingham SC to have spoken about an unspecified incident that would "overshadow" Omagh. On another occasion he referred to a former member of the Foreign Legion named as James Smith from Massachusetts and said: "If you wanted to have Tony Blair assassinated he is your man".
Today's proceedings in the Special Criminal Court dealt with the preliminary hearing in connection with the disclosure of documents relating to the case from the prosecution to Mr McKevitt's defence lawyers.
Among those in the court prepared to give evidence was the British Ambassador to Ireland Sir Ivor Roberts.
There were also two official witnesses from the United States, the assistant director of the counter-terrorism section of the FBI and an FBI field officer.
The hearing was later adjourned until tomorrow. Mr Roberts, who was in court most of the day, was told he would not be required until tomorrow morning at the earliest.
This afternoon's proceedings involved detailed legal argument between the two sides in the case.
PA