Israel says it will prevent, if necessary by force, a nine-ship flotilla of peace activists and humanitarian aid from reaching the Gaza Strip.
The Freedom Flotilla is carrying around 700 pro-Palestinian activists from various countries, as well as 10,000 tonnes of aid.
It is by far the largest fleet of aid to try to reach Gaza since Israel imposed its siege on the coastal territory in 2007.
In accordance with the directions of the Israeli government, the Israel army and the Israeli navy are preparing to prevent the flotilla from reaching the Gaza shore," a military source said on Thursday.
The Israeli army also took journalists on a tour of a detention centre being prepared at Ashdod port for holding the aid activists.
Ma’ariv, an Israeli newspaper, said preparations were being made to provide the detainees with food, drink and medical treatment.
The paper said that Israelis on board would be arrested, Palestinians would be questioned by the Israeli secret service, and foreign nationals would be sent back to their countries.
'Message to Israel'
Hanin Zuabi, a member of the Israeli parliament who is on board the flotilla, told Al Jazeera that the activists intend to reach Gaza regardless of plans to stop them.
"If the Israelis try to stop us, this will be a huge diplomatic and political crises for them," Zuabi said.
"We have 50 states participating in this and are sending a very clear message to Israel - the international community is not accepting the siege on Gaza."
Al Jazeera's Jamal Elshayyal, on board the flotilla, said the activists travelling in the convoy included European parliamentarians, former US diplomats and Nobel peace laureates.
Organisers of the aid fleet said that they will ignore Israeli threats and head straight for Gaza's shores.
Three ships are from Turkey, two from the UK and one each from Ireland, Greece, Kuwait and Algeria.
"Israel should not be under any illusion whatsoever that their threats or intimidation will stop us or even that their violence against us will stop us," Huwaida Arraf, from the Free Gaza Movement, said.
Some Israeli officials see this as a disastrous public-relations situation.
"We can't win on this one in terms of PR," Yigal Palmor, a foreign ministry spokesman, said.
"If we let them throw egg at us, we appear stupid with egg on our face. If we try to prevent them by force, we appear as brutes."
Israel says the blockade of Gaza aims to prevent Hamas, the political movement that controls Gaza, from acquiring weapons or materials that could be used for military purposes.
For the majority of Gaza's population of 1.5 million people, the result has been impoverished living conditions.