Findings of a U.N. commission led by former New Zealand Prime Minister Geoffrey Palmer, which were leaked in Turkey and Israel, indicated the military operation was "premature" and the deaths "unacceptable," the British newspaper The Daily Telegraph reported.
Nine Turkish activists died in May 2010 when Israeli navy commandos stormed the MV Mavi Marmara, the lead ship in a flotilla of vessels bound for Gaza.
Israel was asked to express regret, not apologize, which the nation's leaders hailed as a victory. Turkey was criticized for not doing enough to stop the flotilla and for its link to an Islamist group that helped organize it.
The U.N. findings were expected to be released Thursday, but may be delayed after last-ditch efforts by Israeli and Turkish officials to reach an acceptable compromise, particularly on Israel apologizing for the activists' deaths, failed to materialize, the Telegraph said.
"An apology is not a compromise; it is a humiliation and an abandonment of [Israeli] soldiers," said Foreign Minister Avigdor Lieberman. "We regret the loss of life of people from any nation. There are things we can discuss with Turkey and things we cannot."
Israel already agreed to compensate families of the victims, indirectly through a Turkish government fund, and to issue a statement expressing the regret over the loss of life, the Telegraph reported.