The new effort to break the blockade will test Israel's resolve as it faces a wave of international outrage over its deadly naval raid of another aid ship earlier this week.
Activists on board the Irish boat, including a Nobel Peace Prize laureate, insisted they would not resist if Israeli soldiers tried to take over their vessel. They said they expected the 1,200-ton Rachel Corrie to reach Gaza by late Saturday morning.
Diplomatic fallout and protests across Europe and the Muslim world have increased pressure to end the embargo Israel imposed after the Islamic militant Hamas group seized power in Gaza three years ago. The blockade has plunged the territory's 1.5 million residents deeper into poverty and sharply raised Mideast tensions as the U.S. makes a new push for regional peace.
Israeli Prime Minister Benjamin Netanyahu told his Cabinet on Thursday the Irish boat would not be allowed to reach Gaza. On Friday, Israel's foreign minister said the policy had not changed.
"We have made it clear to the Irish and others, no ship will reach Gaza without a security inspection," Foreign Minister Avigdor Lieberman told Channel 1 TV.
The Cambodian-flagged Rachel Corrie -- named for an American college student who was crushed to death by a bulldozer in 2003 while protesting Israeli house demolitions in Gaza -- was carrying hundreds of tons of aid, including wheelchairs, medical supplies and cement.
This latest attempt to breach the blockade differs significantly from the flotilla the Israeli troops intercepted on Monday, killing eight Turks and an American after being set upon by a group of activists.
Nearly 700 activists had joined that operation, most of them aboard the lead boat from Turkey that was the scene of the violence. That boat, the Mavi Marmara, was sponsored by an Islamic aid group from Turkey, the Foundation for Human Rights and Freedom and Humanitarian Relief. Israel outlawed the group, known by its Turkish acronym IHH, in 2008 because of alleged ties to Hamas. The group is not on the U.S. State Department list of terror organizations, however.
By contrast, the Rachel Corrie was carrying just 11 passengers, whose effort was mainly sponsored by the Free Gaza movement, a Cyprus-based group that has renounced violence.
Irish Nobel Peace Prize laureate Mairead Corrigan told The Associated Press from the ship Friday that the group would offer no resistance if Israeli forces came aboard.
"We will sit down," she said in a telephone interview. "They will probably arrest us ... But there will be no resistance."
Netanyahu has instructed the Israeli military to avoid harming the passengers on board the Irish boat, a participant at Thursday night's Cabinet meeting said. He spoke on condition of anonymity because the meeting was closed.
Foreign Ministry director Yossi Gal urged the activists to dock in the southern Israeli port of Ashdod and promised to transfer all cargo except any weapons or weapons components to Gaza. But the activists resisted the appeal.
Israel has "no desire to board the ship," Gal told reporters. "If the ship decides to sail to the port of Ashdod, then we will ensure its safe arrival and will not board it."
Corrigan said the activists would "not be diverted anywhere else. We head to Gaza in order to deliver the humanitarian aid and to break the siege of Gaza."
The former U.N. humanitarian coordinator in Iraq, Denis Halliday, said from the ship that trade unions and government officials had inspected its cargo. "So we are 100 percent confident that there is nothing that is offensive or dangerous," he told Israel's Channel 2 TV.
Still, he acknowledged that Israel might object to the 500 tons of cement on board, which the army maintains the militants can use to fight it.
In Washington, the State Department said U.S. officials had been in touch with "multiple" countries, including the Israeli and Irish governments, about the latest effort.
"Everyone wants to avoid a repetition of this tragic incident," spokesman P.J. Crowley said.
International condemnation continued Friday, with protests in Syria, Greece, Mauritania, Bahrain and Malaysia, where some demonstrators burned Israeli flags and carried mock coffins. In Norway, the military canceled a seminar scheduled for later this month because an Israeli army officer was to have lectured.
Israel claims activists ambushed the Israeli commandos as they rappelled on board the Mavi Marmara from helicopters on Monday, and the military and Turkish TV have released videotape showing soldiers under attack. Returning activists admitted fighting with the Israeli commandos but insisted they acted in self defense because the ships were being boarded in international waters by a military force.
On Friday, the Israeli military released what it claimed was a radio exchange with the flotilla, in which unidentified male voices were heard making anti-Semitic and anti-American comments. It was impossible to independently authenticate the tape.
The Israeli Defense Forces have been criticized for seizing most video and audio from the Mavi Marmara. The Foreign Press Association, which represents hundreds of journalists in Israel and the Palestinian Territories, demanded Thursday that the military stop using the captured material without permission.
Meanwhile, Hamas leader Ismail Haniyeh said the Islamic militants have refused to accept any aid from the Israeli-intercepted flotilla. "We are not seeking to fill our (bellies), we are looking to break the Israeli siege on Gaza," he said.
The standoff has particularly strained Israel's relationship with once-close ally Turkey.
Turkish Prime Minister Recep Tayyip Erdogan kept up the tough rhetoric on Friday, telling a crowd that "nobody should test Turkey's patience."
And Deputy Prime Minister Bulent Arinc announced Turkey was downsizing its economic and defense cooperation with Israel.