Israel must make amends to be forgiven for a commando raid on a Gaza-bound aid flotilla, including apologizing and paying compensation, Turkish President Abdullah Gul told the French daily Le Monde.
Gul added that if Israel made no move to heal the rift, then Turkey could even decide to break diplomatic relations.
In an interview published on Friday, Gul said the Israeli raid at the end of May, which killed nine activists, was a "crime" which might have been carried out by the likes of al-Qaeda rather than a sovereign state.
"It seems impossible to me to forgive or forget, unless there are some initiatives which could change the situation," Gul was quoted as saying by Le Monde.
Asked what these might be, he said: "Firstly, to ask pardon and to establish some sort of compensation." He added that he also wanted to see an independent inquiry into the botched raid and a discussion on lifting Israel's blockade of Gaza.
Asked if Turkey might break relations with Israel if they did nothing, Gul said: "Anything is possible."
Once a close ally of Israel, Turkey recalled its ambassador following the flotilla incident, cancelled joint military exercises and said trade and defense deals worth billions of dollars would be reduced to a minimum.
Separately, Philip Alston, the UN special rapporteur on extra-judicial executions, said any inquiry set up by Israel to investigate the Gaza flotilla incident "must be given a genuine capacity to find the facts" or it would not be credible.
To comply with international standards, he said, such an inquiry would have to be independent of the government and have full legal authority to obtain direct access to all relevant evidence, including the military personnel involved.
Israel has fended off a UN demand for an international investigation, instead accepting a US proposal for an Israeli inquiry with the participation of outside observers.