Speaking today on NBC’s Today Show, Secretary of State John Kerry warned Israel against following through with suggestions they might try to sabotage the Iran nuclear deal with the P5+1 by unilaterally attacking Iran, saying it would be an “enormous mistake.”

Kerry said he thinks attacking Iran isn’t necessary and that doing so would be “a huge mistake with grave consequences for the region,” which would give Iran a reason to begin actively trying to create nuclear weapons, to defend against nuclear-armed Israel.

Kerry also mocked Israeli calls for Iran to have no civilian nuclear program at all, saying Iran’s nuclear material is “not something that you can flush down the toilet,” he further warned that Israel’s lobbying against the Iran deal in the US Congress risked them getting blamed if the deal is blocked by Congress.

Former Israeli Ambassador to the US Michael Oren, now an MP in Israel’s ruling coalition, spurned Kerry’s comments, saying Israel wouldn’t be “threatened” into backing off on its position on the deal. Oren went on to say Israel had a “national duty” to oppose the Iran pact, and do anything it can to prevent it from being finalized.

How serious Israeli threats to attack Iran outright are is unclear, of course. Prime Minister Benjamin Netanyahu insisted, on the day the deal was announced, that he didn’t feel Israel was “bound” by the pact, and it wouldn’t stop them taking any action, including military action. At the same time, Israel has been threatening to attack Iran for decades now, and has never actually done so, so this may just be the usual bluster.