Hussein Uruc, a leader of IHH (Foundation for Human Rights and Freedoms and Humanitarian Relief) confirmed to Israel's Ynetnews that the flotilla, planned for late June, may be canceled in light of turmoil in Syria and elsewhere. The story was first reported by the Turkish newspaper Hurriyet.
He said a decision will be made Thursday, while other groups said they will take part regardless.
Israeli commandos boarded the ship Mavi Marmara on May 31, 2010, killing nine people, and seized the other boats.
"The IHH have their own reasons, internal reasons. It won't stop us from going," Israeli emigre Dror Feiler, leader of the Free Gaza movement in Sweden, said. "... We shall be sorry if they can't go, but it doesn't pose a threat to the flotilla.
"Maybe this is a blessing in disguise. Thus far Israel has claimed that the Turks are terrorists. What will they say now -- that the Swedes, Danes, Americans and all the world's nations are all terrorists?"