PRESIDENT OBAMA’S acknowledgment that “we don’t have a strategy yet” in Syria understandably attracted the most attention after his perplexing meeting with reporters Thursday. But his restatement of the obvious was not the most dismaying aspect of his remarks. The president’s goal, to the extent he had one, seemed to be to tamp down all the assessments of gathering dangers that his own team had been issuing over the previous days.

This argument with his own administration is alarming on three levels.

The first has to do with simple competence. One can only imagine the whiplash that foreign leaders must be suffering. They heard U.S. Ambassador to the United Nations Samantha Power denounce Russia as “today . . . they open a new front . . . Russia’s force along the border is the largest it has been . . . the mask is coming off.” An hour later, Mr. Obama implicitly contradicted her: “I consider the actions that we’ve seen in the last week a continuation of what’s been taking place for months now . . . it’s not really a shift.”

Similarly, his senior advisers uniformly have warned of the unprecedented threat to America and Americans represented by Islamic extremists in Syria and Iraq. But Mr. Obama didn’t seem to agree. “Now, ISIL [the Islamic State of Iraq and the Levant] poses an immediate threat to the people of Iraq and to people throughout the region,” he said. “My priority at this point is to make sure that the gains that ISIL made in Iraq are rolled back.” Contrast that ambition with this vow from Secretary of State John F. Kerry: “And make no mistake: We will continue to confront ISIL wherever it tries to spread its despicable hatred. The world must know that the United States of America will never back down in the face of such evil.”

The discrepancies raise the question of whether Mr. Obama controls his own administration, but that’s not the most disturbing element. His advisers are only stating the obvious: Russia has invaded Ukraine. The Islamic State and the Americans it is training are a danger to the United States. When Attorney General Eric H. Holder Jr. says the threat they pose is “in some ways . . . more frightening than anything I think I’ve seen as attorney general,” it’s not because he is a warmonger or an alarmist. He’s describing the world as he sees it. When Mr. Obama refuses to acknowledge the reality, allies naturally wonder whether he will also refuse to respond to it.

Which is, in the end, the most disturbing aspect of Mr. Obama’s performance. Throughout his presidency, he has excelled at explaining what the United States cannot do and cannot afford, and his remarks Thursday were no exception. “Ukraine is not a member of NATO,” he said. “We don’t have those treaty obligations with Ukraine.” If Iraq doesn’t form an acceptable government, it’s “unrealistic” to think the United States can defeat the Islamic State.

Allies are vital; the United States overstretched in the Bush years; it can’t solve every problem. All true. But it’s also true that none of the basic challenges to world order can be met without U.S. leadership: not Russia’s aggression, not the Islamic State’s expansion, not Iran’s nuclear ambition nor China’s territorial bullying. Each demands a different policy response, with military action and deterrence only two tools in a basket that includes diplomatic and economic measures. It’s time Mr. Obama started emphasizing what the United States can do instead of what it cannot.