A group of Lebanese women activists joined by Europeans and journalists are planning to sail for Gaza in the latest bid to break Israel's blockade of the coastal enclave.
International fury and condemnation erupted after Israeli soldiers stormed a six-ship aid flotilla heading for Gaza on May 31, killing eight Turks and a Turkish-American on board.
Israeli leaders say the troops acted in self-defence after the flotilla activists attacked them.
But preliminary autopsy reports revealed that the nine activists were shot a total of 30 times, some in the back of the head or in the back.
The head of the UN criticised Israel's investigation into the attack and said the inquiry lacked international credibility.
The UN wants its own investigation, but Israel is refusing.
Meanwhile, the Lebanese group Hezbollah has denied it was backing the all-women aid flotilla, saying it did not want to give Israel a pretext to attack peaceful aid activists.
"Hezbollah confirms that it decided from the very beginning to stay away from this humanitarian act in terms of organisation, logistic support and participation so as not to give the Israeli enemy any pretext to attack the participants," Hezbollah said in a statement.
"Hezbollah firmly believes this peaceful, civilian effort will succeed.
The organisers had not announced a departure date for the ship, christened Mariam in honour of the Virgin Mary.
Following international outcry, Israel said on Thursday that it was easing the land blockade on Gaza, which for the past three years has been controlled by a Hamas-led government.
But it said the sea blockade would continue.
The International Committee of the Red Cross said that the blockade was illegal and described it as a violation of the Geneva Conventions.