The Tánaiste is on his way to Lebanon this morning where he will meet members of the 121st UNIFIL Infantry Battalion.
23-year-old Private Seán Rooney, who was killed there before Christmas, was part of that unit.
Micheál Martin will reiterate to Lebanese officials that the Irish Government wants "all of the facts" and to ensure that those responsible are "brought to justice."
The Minister for Foreign Affairs will be accompanied by the Secretary General of the Department of Defence and the Chief of Staff of the Defence Forces.
As well as visiting the personnel of the 121st Infantry Battalion, the Tánaiste will also meet the United Nations Under-Secretary-General for Peace Operations, as well as the Lebanese Minister for Defence.
Speaking ahead of the visit, Micheál Martin said that it will be an opportunity for him to convey his sympathies and those of the Irish Government to the colleagues of Private Seán Rooney on their loss.