President Trump told his cabinet on Wednesday that President Volodymyr Zelensky of Ukraine was expected to come to Washington to sign a framework agreement enabling the United States to share in the country’s mineral wealth, but he insisted the United States would not be providing security guarantees to Ukraine in return.

Obtaining such guarantees from Washington, the only nuclear-armed power truly capable of standing up to Russia, had been Mr. Zelensky’s central demand. His greatest concern is being forced into a cease-fire, only to discover Russia uses the time to rebuild its military, regroup and attempt to seize his country again.

But Mr. Trump made clear that if there are to be any such promises, they will have to come from Europe, with little backup from Washington.

“I’m not going to provide security guarantees beyond very much,” he said at his first cabinet meeting, which was dominated by discussion of the firing of government workers and other efforts being overseen by Elon Musk, who has taken an outsized role in the administration. “We’re going to have Europe do that.”

Mr. Trump had not spoken publicly about what role, if any, the United States would play in deterring Russia from one day restarting the conflict. He stood in silence on Monday when Emmanuel Macron, the president of France, repeatedly brought up the topic of security guarantees at a joint news conference at the White House.

Mr. Trump’s flat statement that the United States would not be party to any security guarantees may accelerate an end to the fighting, but ultimately could embolden President Vladimir V. Putin of Russia. The Russian leader is far more likely to agree to a cease-fire if he knows that the United States would not step in should he change his mind and attack again.