As chaos continues to reign in and around Kabul’s airport, President Biden sought to reassure the world on two points. First, that, though the mass evacuation from Afghanistan that his decision to pull out U.S. troops catalyzed is difficult, the military has matters well in hand, with flights already having taken out 13,000 U.S. citizens and other civilians since Aug. 14 and resuming Friday after an hours-long pause. Second, he said that the airlift, which he called “one of the largest and most difficult in history,” would encompass not only U.S. citizens and those of Western nations, not only Afghans who directly assisted the U.S. military and other agencies, but also “vulnerable Afghans such as women leaders and journalists."

That broad “commitment” — Mr. Biden’s word — is crucial. It’s the minimum that U.S. credibility and, to be sure, basic human decency require. It is to Mr. Biden’s credit that he would voice it. What’s far less certain, unfortunately, is whether, at this late date, just 11 days before the president’s self-imposed Aug. 31 deadline for total withdrawal of U.S. troops, the means to fulfill it are in place or even contemplated.

The administration still does not have a headcount of Americans who need to get out, much less of “vulnerable Afghans" — though the latter number probably runs to six figures. On Friday, he reiterated his belief that the violence-prone Taliban fighters manning the perimeter of the U.S.-controlled airport will let American passport holders through, per an understanding with the United States, but even so they must run a dangerous gantlet to get there. As for “vulnerable Afghans,” by definition, they dare not risk it.

The president still seems reluctant to take bolder steps, such as extending the military perimeter around the airport or sending U.S. special forces into the city to collect evacuees, as the British and French governments apparently have done. Nor would he abandon the Aug. 31 deadline, saying instead — and contrary to apparent logistical reality — that it might still be met.

Mr. Biden offered some happy talk about the U.S.'s undamaged credibility with “united” U.S. allies. “This is about America leading the world,” he said. “And all our allies have agreed with that.” These jarringly self-congratulatory remarks seemed hard to reconcile with reality, too, given the allies’ well-known misgivings about his administration’s handling of the Afghanistan withdrawal. He nevertheless still has a chance to keep those words from ringing hollow through history — by delivering on the commitment to rescue not only Americans and those Afghans who directly aided this country, but also at least a large portion of those who trusted in democratic freedom itself and face Taliban reprisals as a result.

Alas, if Mr. Biden is prepared to commit the resources, civilian and military, and time required to complete that mission, he gave no indication of it Friday.