Israel has informed the United Nations and - through diplomatic channels - the Lebanese government that it reserves the right to use all means necessary to stop ships seeking to breach the naval blockade on the Gaza Strip.

Israel began a massive diplomatic effort Wednesday to convince the Lebanese authorities to prevent an aid ship from trying to breach the blockade on Gaza.

The diplomatic efforts are designed to prevent the departure of at least one vessel, carrying 50 to 70 Lebanese women and food aid. Israel has been in touch with the UN, United States, France, Spain and Germany. It has also been speaking with the Vatican because the ship is expected to include several dozen Catholic nuns.

Israel has also asked Egypt to prevent a planned Iranian aid ship bound for Gaza from passing through the Suez Canal.

In a letter to Secretary-General Ban Ki-moon, Israel warned that the attempt by the organizers to sail from Lebanon and deliver humanitarian aid to Gaza could escalate tensions and affect peace and security in the region.

"Israel reserves its right under international law to use all necessary means to prevent these ships from violating the existing naval blockade imposed on the Gaza Strip," wrote Israel's ambassador to the UN, Gabriela Shalev.

"The organizers of these boats have made repeated assertions to the media that they wish to be shaheeds [martyrs]," Shalev added, noting that Israel believes that "there exists a possible link between the organizers of the ships in question and the terrorist group Hezbollah."

On Friday the Lebanese Shi'ite movement Hezbollah said it would not take part in Gaza-bound aid missions so as not to give a pretext for Israel to attack Lebanon.

"We in Hezbollah highly value the humanitarian moves to break the siege on Gaza, but since the beginning we have stayed away from such acts not because we are greedy but because we do not want to give the Israeli enemy an excuse to carry out an aggression against Lebanon," the group said in a statement.

The statement came after local media said Hezbollah was urged not to give Israel a pretext to attack by supporting aid ships leaving from Lebanon for Gaza.

Israeli defense officials said in response they still believe that Hezbollah was behind the Lebanese aid flotilla planned to set sail for Gaza today.

On Friday, the Lebanese newspaper Al-Liwaa quoted an anonymous Lebanese source as saying that the Public Works and Transportation Ministry has asked Hezbollah to refrain from participation in the Lebanese aid ship Miriam.

The group of women, who announced that they do not belong to any political group, will sail from the northern Lebanese port city of Tripoli to Cyprus and then to Gaza.

In Israel there is still uncertainty about the exact plans or schedule of the aid ship or ships leaving from Lebanon. Contradictory information was released to the Lebanese media by the Lebanese organizers of the flotilla, but the launch is expected today or tomorrow.

The Israel Defense Forces is planning for the possibility that it will have to block the flotilla; military sources say their orders from the political leadership are to block ships from breaching the blockade.

Military sources say they are preparing for any eventuality, but the hope is that the activists will not behave like those on the Turkish ship the Mavi Marmara when Israeli commandos boarded late last month. The hope is that the activists will behave passively like those on another ship, the Rachel Corrie.

Meanwhile, Ban Ki-moon urged Israel to agree to an international investigation into the takeover of the Mavi Marmara on May 31, which resulted in the death of nine activists.

The UN chief said he is encouraged that Israel is reviewing its Gaza policy and recently decided to allow more goods into the Strip.

Defense Minister Ehud Barak, who left for the United States last night, will meet with Ban and ask him to withdraw his demand for an international inquiry.