Israel's UN envoy has told the world body that Israel is entitled to use "all necessary force" to prevent activists sailing from Lebanon to Gaza.
In a letter to Secretary General Ban Ki-moon, Ambassador Gabriella Shalev said Israel suspects the organisers may be linked to Lebanon's Hezbollah.
A group of Lebanese women activists is planning to sail to Gaza on a ship with medical supplies in a new bid to break Israel's four-year blockade of the Palestinian territory.
Hezbollah denies backing the aid flotilla saying that it didn't want to give Israel a pretext to attack the activists.
Israel is under pressure after it seized an aid flotilla in May, killing 9 Turkish activists during the operation.