Israeli officials have threatened to abandon the UN international probe into the Gaza flotilla killings tonight, following comments from UN Secretary-General Ban Ki-moon insisting that they had not, in fact, agreed to grant blanket immunity to all Israeli commandos from testifying.

Israeli officials had claimed a secret deal existed with Ban earlier today, which prompted Ban to issue the formal denial. They now say their participation in the panel was predicated on this alleged deal, and that if it doesn’t exist they may indeed abandon it entirely.

The probe is looking into the Israeli attack on the Mavi Marmara aid ship, an attack which left nine aid workers dead. Israel has insisted that the probe will vindicate the killings, and prove that the entire incident is Turkey’s fault. It will also look into Israeli allegations that the charity group responsible for the ship was secretly in league with terrorists.

It came as something of a surprise when Israel announced its last-minute acceptance of the probe last week, after weeks of insisting that even the suggestion of an international probe was an insult. It also made put the US in the difficult position of having called for a probe in early June, abandoned the call over Israeli objections, then accepted it again. If Israel decides to abandon the probe yet again, it would likely leave the US trying to backpedal into condemning the international probe once again.