Israeli gunships were standing by today to stop a flotilla of pro-Palestinian activists from reaching the Gaza Strip, setting the stage for what could become a dramatic showdown on the high seas.

Foreign minister Avigdor Lieberman said the country was prepared to stop the flotilla "at any cost".

He called the aid mission a provocation and urged the international community to show understanding for the tough response.

"We really have all determination and political will to prevent this provocation against us," he said. "I think that we're ready at any cost ... to prevent this provocation."

Military officials said an initial group of gunships went out to sea yesterday to prepare for the flotilla's arrival. But plans to dispatch additional gunships were put on hold after reports that the flotilla had encountered mechanical problems.

The officials said the gunships would remain in port until the flotilla got closer.

The military said it would intercept the ships, escort the vessels to shore and give the activists the choice of deportation or going to jail.

Israel says that after a security check, it will transfer the cargo to Gaza through the United Nations.

Officials say they hope the situation will be resolved peacefully, but are prepared to use force if necessary. Masked naval commandos have been trained for the mission and Israel has built a large makeshift detention centre in a southern port to process the activists.

The activists, among them a Nobel peace laureate, are trying to draw attention to a three-year-old Israeli blockade of the Gaza Strip imposed after Hamas militants violently seized control of the territory. They say they are carrying tons of desperately-needed humanitarian aid.

Greta Berlin, one of the organisers of the effort, said a total of seven ships were heading to Gaza after an eighth vessel suffered a malfunction and had to turn back.

The organisers' website said the flotilla remained off the southern coast of Cyprus, 250 miles north west of Gaza, last night. She said the flotilla would resume the journey today. It was unclear when they would reach Israeli waters, she added.

The ships originally embarked from Turkey, Greece and other European ports.

Israel says the Gaza blockade is needed to prevent Hamas, which has fired thousands of rockets into Israel, from rearming.

It rejects claims that a humanitarian crisis is brewing in Gaza, saying it allows more than enough food and medicine into the strip.

Critics, however, say the blockade has crushed Gaza's economy, eliminated some 100,000 jobs and prevented the territory from repairing the destruction caused by an Israeli military offensive early last year.

Israel has reached out to its Mediterranean neighbours to stop the flotilla from approaching. Turkey, whose president has harshly condemned Israel's Gaza offensive, has rejected the gesture.

A Turkish charity is spearheading the aid mission and Turkish authorities have refused to intervene.

But yesterday Cyprus said it was banning any ship from sailing to Gaza from its shores because organisers of a flotilla trying to break a blockade of the Palestinian territory ignored a government appeal not to involve the island.

Acting government spokesman Titos Christofides condemned the Israeli blockade and expressed solidarity with the Palestinian people, but said the appeal was made to protect the island's "vital interests".

This is the ninth time that the Free Gaza Movement, the pro-Palestinian organisation behind the effort, has sent a flotilla of supplies to Gaza.

Israel allowed five deliveries to reach Gaza, but has not allowed any ships through since its military offensive, which ended last January.

Among the passengers are Nobel Peace Prize laureate Mairead Corrigan Maguire, former US Rep Cynthia McKinney, a Holocaust survivor in her 80s, a retired US army colonel and politicians from a dozen European countries.