Israel’s missile strikes on a Syrian air base Monday are a stark warning that this war could yet turn into a regional conflagration — and added reason for President Trump to draw a line to prevent that outcome.

The pre-dawn attack on the airfield, which also hosts Iranian militias, came hours after the Syrian regime’s deadly chemical attack on civilians in a rebel-held town near Damascus.

Trump says “nothing is off the table” when it comes to a response to the latest atrocity. But, as we noted Monday, it’s clear that something more than a one-off strike by American missiles is needed.

After all, Syrian ally Russia is insisting the reports of the chem attack, which has forced the evacuation of the town, are themselves a “provocation,” and denouncing the Israeli strike as a “dangerous development.”

In fact, the real danger lies in Iran’s bid to establish a permanent presence in Syria — which Israel just showed it won’t accept. (After all, Tehran regularly vows to destroy the Jewish state.)

Don’t look to the “international community” to stop this madness: Syria next month will chair a UN forum on nuclear and chemical disarmament. And of course Russia regularly uses its Security Council veto to protect both the Syrian and Iranian regimes.

The Moscow-Tehran-Damascus alliance has routinely targeted hospitals and schools. President Bashar al-Assad’s regime has tortured captives on a mass scale.

But they haven’t won yet: The US-allied forces that have ISIS nearly finished still control Syria east of the Euphrates, a region that holds most of the nation’s oil. A Washington-declared no-fly zone can let them hold on, denying Iran control of the entire northern Middle East.

If the United States instead lets Assad & Co. steal the fruits of the victory over ISIS, Iran will move on to its next targets — and the whole region will stand on the edge of war.