Israel is being warned to act with "absolute restraint" when the MV Rachel Corrie approaches Gaza.
The ship - with three Irish citizens on board - was part of the original flotilla intercepted by Israeli forces yesterday.
It is due to arrive in Gaza tomorrow evening.
The Foreign Affairs Minister Micheál Martin has discussed the ship's approach with the Israeli Ambassador to Ireland.
Two Irish citizens who were detained by the Israeli authorities yesterday, are due back in Ireland tonight.
The Irish-Malaysian MV Rachel Corrie, is off the coast of Libya and on board are:
:: Denis Halliday, former assistant secretary-general of the United Nations. After more than 30 years in the UN, Kofi Annan appointed him Humanitarian Coordinator in Iraq in 1997. He has been a strong opponent of the war in Iraq.
:: Electrician Derek Graham, who has been on four of the five voyages which landed in Gaza, and his wife Jenny from Mayo. Both are members of the Free Gaza movement.
:: Nobel peace prize winner Mairead Maguire. She was detained last year after attempting to get into Gaza with a boat load of aid and this is her third humanitarian trip to the Palestinian territories.