An Israeli warship attempted to stop a Libyan aid vessel trying to breach the Gaza blockade tonight.
But the Moldovan-flagged Amalthea, which left Greece on Saturday carrying 2,000 tons of food and medical supplies, refused to alter its course for el-Arish in Egypt and insisted it will steam on for Gaza.
The Gadhafi International Charity and Development Foundation said the Israelis were shadowing the ship.
The Israeli military confirmed that it has made contact with the Amalthea and said "the navy has begun preparing to stop the ship".
The latest challenge to Israel's blockade on the seaside strip came more than a month after Israeli commandos boarded a flotilla of Gaza-bound ships, killing eight Turks and a Turkish-American on one of the vessels.
That raid focused international attention on the Israeli embargo on Gaza, which is ruled by the Islamist militant group Hamas, and forced Israel to ease the movement of goods through land crossings.
However, Israel's naval blockade on the territory, meant to keep weapons from reaching Hamas militants, remains in place.
Israeli's policy has been to offer aid ships sailing for Gaza the option of docking at an Israeli port, after which Israel would screen the goods aboard and transfer them into Gaza by land.
An Israeli government spokesman repeated that offer today, inviting the activists aboard the Amalthea to sail to the Israeli port of Ashdod and unload there.
"We will guarantee delivery of all civilian cargo to the people of Gaza," he said. "There are no limitations whatsoever on food reaching the people of Gaza. The crossings are open."
Meanwhile today Turkish Foreign Minister Ahmet Davutoglu said the country will keep pushing for an international inquiry into the Israeli raid on Gaza-bound ships that left nine activists dead.
The comments come a day after an Israeli report concluded that flawed intelligence-gathering and planning led to the botched operation.
Ties between Turkey and Israel - once close allies - reached a new low following the May 31 raid.