IT’S NOT YET clear whether reports of the use of chemical weapons in Syria by the regime of Bashar al-Assad are correct; if they are, a red line drawn by President Obama will have been crossed. What’s certain is that the Syrian crisis has already passed what should be another tipping point for U.S. intervention: what a top U.N. official calls a “staggering acceleration” of refugees that threatens to destabilize much of the Middle East.

In December, the number of Syrians fleeing the country to Turkey, Lebanon, Jordan and Iraq averaged 3,000 a day, according to António Guterres, the U.N. high commissioner for refugees. In January, the daily average rose to 5,000; in February, it was 8,000. Now there are days when 14,000 desperate civilians cross the border, Mr. Guterres told us. The total number of registered refugees is now more than 1.1 million, and the United Nations expects it could reach 3 million by the end of this year — or 50 percent more than left Iraq after 2003.

“This is becoming a real threat to regional peace and security to an extent that was not obvious in the beginning,” Mr. Guterres said. “There could be an explosion in the area that the international community would have no tools to cope with.”

Why an explosion? Consider Lebanon, an already unstable nation that, as with its neighbor Syria, is riven by sectarian tensions. Mr. Guterres estimates that about 400,000 Syrian refugees are spread across 900 communities — a number equal to 10 percent of Lebanon’s population. Most of them are Sunnis, and resentment against them by Lebanon’s Shiite, Christian and Druze populations is growing. There have been clashes between Sunni jihadists and the Shiite militia Hezbollah, and air attacks by Syrian government forces along the border. The eruption of a full-scale sectarian conflict in Lebanon mirroring that of Syria is all too easy to foresee.

Then there is Jordan, a close U.S. ally already afflicted by serious economic problems, which has taken in 360,000 refugees. Nearly 100,000 are in the Zaatari refu­gee camp, where security problems are growing. Jordan’s own population is restless over economic conditions, and there were mass protests last year over price increases. How or whether the country of 6 million will cope with 1 million refugees, if the forecasts for 2013 prove correct, is anyone’s guess.

Part of addressing the refu­gee crisis boils down to funding. Mr. Guterres says his agencies and others serving the refugees have about 20 percent to 30 percent of what they need to do their jobs. The United States is the largest contributor, having provided $385 million for humanitarian assistance, but far more is needed.

No amount of money will alleviate the Syrian refu­gee crisis, however, if more is not done to stop the carnage that is causing it. Mr. Guterres told us that if the Assad regime does begin to use its chemical weapons, humanitarian assistance would cease in Syria. That’s one more reason why Mr. Obama must accelerate efforts to bring about the regime’s downfall — and respond quickly and forcefully if chemical weapons have been used.