Technical problems have been blamed for the decision by Turkish activists not to send a ship in a flotilla to Gaza later this month.
The president of the Islamist group IHH, Bulent Yildirim, said they would not be able to participate.
However a member of the group Free Gaza said the flotilla would still set sail without the IHH boat but with around ten others from a range of pro-Palestinian groups.
IHH also organised last year's flotilla, which saw nine activists killed during clashes with Israeli commandos.