McKevitt wanted his new terror organisation's first strike to be bigger than the Omagh bomb atrocity, a court heard yesterday.
The allegations were made at the Special Criminal Court by FBI agent David Rupert, the key prosecution witness in the trial of the man accused of masterminding the dissident republican group behind the August 1998 Omagh attack, which killed 29 people and two unborn babies, and injured hundreds more.
He told how McKevitt, 53, planned to build a new terror group with members of the Real IRA, the Continuity IRA, the INLA and some disaffected provisionals.
McKevitt, of Dundalk, Co Louth, is the first person in Ireland to be charged with directing terrorism. He is also accused of membership of the Real IRA. He has pleaded not guilty to both charges.
The prosecution is centred on the evidence of Mr Rupert, a US trucking boss turned double agent for the FBI and MI5. After allegedly infiltrating the dissident group in 1999, he said he met McKevitt on several occasions.
At one meeting, Mr Rupert claimed McKevitt told him he had two sleeper agents in place in America. One of these was named as James Smith.
Mr Rupert said: "I was told that he was ex-French Foreign Legion and he was particularly good with weapons."
McKevitt, alleged to be the former quartermaster in the Provisional IRA, had worked with Smith on a weapons acquisition trip to South Africa.
"I was told that he was of a level of profession that in the event that they 'they' being the new army wanted to assassinate somebody of the type of Tony Blair, that he would be the type of person they would bring in to do it," said Mr Rupert.