The exact location of the boats as they approach the Gaza coastline will be kept a secret by those aboard, which will include European parliamentarians and the sister-in-law of ex-British Prime Minister Tony Blair, to lessen the chances of their being intercepted, shot at, and possibly arrested by Israeli authorities.

On Tuesday 45 members, comprising 15 nationalities, of the California-based Free Gaza Movement, will leave a port in Cyprus and sail 230 miles south to Gaza.

"We want to bring it to the world's attention that Gaza is virtually an outdoor concentration camp," Greta Berlin, a spokeswoman for the Free Gaza Movement, told AFP.

The organization raised about $300,000 to finance the trip and the vessels are loaded with humanitarian aid specifically for children.

Gaza has been virtually sealed off by land, air and sea and subject to a strict Israeli and international embargo since Hamas routed the forces of the Palestinian National Authority in June of last year during a power struggle.

This has lead to a humanitarian disaster as Israel allows only a trickle of humanitarian goods into the coastal territory.

Those on board will include three European parliamentarians, holocaust survivor Heddy Epstein, Jeff Halper, an Israeli and member of the Israeli Committee Against House Demolitions, Lauren Booth, the sister of Cherrie Blair, and a number of journalists and human rights activists.

Ex-U.S. President Jimmy Carter's Carter Center has backed the voyage as has former anti-Apartheid activist and Nobel Laureate winner, South African Bishop Desmond Tutu.

Tutu told the media, "Peace and security we discovered in South Africa do not come through the barrel of a gun. I support the boat-convoy in its effort to bring humanitarian relief to the people of Gaza."

A Gaza movement spokesperson told the assembled media: "We want to break the siege of Gaza. We want to raise international awareness about the prison-like closure of the Gaza Strip and pressure the international community to review its sanctions policy and end its support for continued Israeli occupation. We want to uphold Palestine's right to welcome internationals as visitors, human rights observers, humanitarian aid workers, journalists, or otherwise."

"We are these human rights observers, aid workers, and journalists. We have years of experience volunteering in Gaza and the West Bank at the invitation of Palestinians," the spokesperson said, and added: "But now, because of the increasing stranglehold of Israel's illegal occupation of Palestine, many of us find it almost impossible to enter Gaza, and an increasing number have been refused entry to Israel and the West Bank as well. Despite the great need for our work, the Israeli government will not allow us in to do it."

Prior to the boat leaving, survivors of the original USS Liberty, after whom one of the boats was named, an American surveillance ship that was attacked and sunk off the coast of Egypt by Israeli security forces during the 1967 Arab-Israeli war, leading to the death of 34 American serviceman, asked the siege-breakers to remember the dead Americans.

"What is the possibility of you and the crew of the SS Liberty throwing 34 long-stemmed roses into the sea as a memorial to the 34 Americans killed aboard the USS Liberty?" asked a spokesman for the survivors.

"We will pay for the roses or whatever else you have in mind. The survivors of the Liberty and their families would be eternally grateful to you and your shipmates for this gesture as no one has ever done anything like this before," he added.

Survivors accuse Israel of deliberately targeting the spying vessel. Israel denies this.

Cypriot authorities expressed concern about the mission of the two boats and their departure from Cypriot waters, but told their Israeli counterparts there was nothing they could do to prevent the expedition.

Israeli authorities are worried about the activists' arrival, the time of which they are unsure. They are also apprehensive as to the seriousness of those aboard and the possibility of a major PR disaster as Israel's navy is responsible for ensuring the continued blockade of the "special security zone" off the Gaza coastline.

However, activists have stated that they are not entering Israeli territorial waters and under international law the Gaza Strip is not part of Israel.

Furthermore, following Israel's supposed pull-out from Gaza in 2005, and the alleged ending of the occupation Israel has no right to be in the vicinity, they say.

Although the Israelis pulled their settlers out from Gaza and withdrew most of their forces, under international law the territory is still considered occupied, as the Jewish state continues to control the borders, airspace, coastline, population registry, electricity and water, in addition to carrying out regular military incursions into the Strip.

Those on board will clearly aim for a confrontation with the Israeli authorities in order to bring international attention to the plight of Gazans.

The Israelis are considering several options. One is to simply allow the vessels to reach Gaza thereby foiling the organizers' apparent desire for a clash. The other is to stop the boats and arrest those on board, risking a nasty confrontation and more unwelcome negative publicity.

The Palestinians in Gaza, however, are looking forward to their successful arrival and have prepared a victory welcoming committee.