Mr Ken Maginnis, the Ulster Unionist security spokesman, will take part in a TV debate next week with Mr Martin McGuinness, Sinn Fein's senior negotiator. Ulster Unionists have traditionally declined to appear with Sinn Fein spokesmen.
BBC 2 television's Newsnight programme next Tuesday will feature a "ground-breaking debate" between the two men, the programme's deputy editor, Ms Karen O'Connor, said, adding that she was looking forward to a "historic discussion".
Mr Maginnis confronted the Sinn Fein president, Mr Gerry Adams, on American television in 1994, but the Newsnight debate will be the first time for the two parties on British television.
Confirming his intention to appear on the programme, Mr Maginnis said yesterday: "I have always felt it is incumbent upon Ulster Unionists to ensure that the IRA message does not go unchallenged. Sometimes I've felt we've been less effective than we should have been. But I am not going to debate this issue for the next five days until the debate."
A spokesman for Sinn Fein said the party hoped for "positive contributions". Mr McGuinness would not take part in the debate with "acrimony and recrimination". However, Sinn Fein said it was "unfortunate" the debate had taken so long to take place.
The announcement follows delicate negotiations between the Newsnight team and the two parties that finally produced results last month. At that time senior UUP officials agreed in principle to the debate, following criticism that Sinn Fein had moved ahead in its propaganda campaign.