IT’S BEEN seven weeks since Secretary of State John F. Kerry charged that Syrian dictator Bashar al-Assad was waging “a war of starvation.” Hundreds of thousands of people in areas controlled by rebel forces were under siege by the government, which was refusing to allow in supplies of food and medicine. “The world must act quickly,” Mr. Kerry warned, because the regime’s tactics “threaten to take a humanitarian disaster into the abyss.”

Since then, there has been no action — not by “the world” nor by the United States, which possesses the means to break the siege but chooses not to employ them. The consequence is that Syria, as winter begins, has descended into Mr. Kerry’s abyss.

Consider the Dec. 4 report by Valerie Amos, the United Nations’ humanitarian coordinator: Seven million Syrians, or 40 percent of the population, are in urgent need of food and medical assistance. By year’s end, 3 million will be refugees in neighboring countries. Only a fraction of those in need are getting international aid.

Some 290,000 people are in besieged areas near Damascus that have been cut off from food and medicine for more than six months. According to Human Rights Watch, “people are suffering from an increasingly severe shortage of food and . . . are dying from lack of medical care because of the siege.” Residents told investigators in telephone interviews that they were eating tree leaves.

Mr. Kerry, who devoted most of the past two weeks to shuttling unsuccessfully between Israelis and Palestinians, hasn’t shown much interest in Syria’s human catastrophe since writing an op-ed about it that was published Oct. 25. U.S. policy has narrowed to extracting the Assad regime’s chemical weapons from the country and promoting a peace conference next month in Switzerland. A strategy once supported by Mr. Kerry of bolstering the rebels has all but collapsed, along with the moderate forces it was aimed at; the administration is now forced to talk to an Islamist coalition that has overtaken its allies.

Mr. Kerry’s strategy is for the peace conference to agree on a transitional government with representatives from all sides. Always a long shot, this goal is now quixotic. With no following on the ground, moderate opposition leaders lack the standing to propose such a coalition, while both the regime and the Islamist groups reject the idea. Russia and Iran, which have helped the Assad forces win a series of tactical military victories in recent months, show no sign of withdrawing their support.

The peace conference has become a fig leaf concealing the absence of a U.S. strategy for Syria — and it is not scheduled to begin for six weeks. During that time thousands more Syrian civilians will undoubtedly die of hunger, exposure or a lack of medicine, when they are not killed by the regime’s indiscriminate shelling and bombing. The United States has options it has not used: It could demand that Russia stop blocking a U.N. Security Council resolution ordering the Assad regime to allow relief convoys as the price of going forward with the conference, which was Moscow’s initiative. It could threaten missile and air strikes on the forces that are conducting the sieges.

“The world cannot sit by watching innocents die,” Mr. Kerry wrote. Yet that’s exactly what he and the Obama administration are doing.