U.S. is preparing more sanctions against Russia, the national security adviser says.

President Biden’s national security adviser said on Sunday, days after Mr. Biden attended his first face-to-face summit meeting with President Vladimir V. Putin, that the United States was preparing more sanctions against Russia in response to the poisoning of Aleksei A. Navalny, the country’s most prominent opposition leader.

“We are preparing another package of sanctions to apply in this case,” Jake Sullivan, the national security adviser, said on CNN’s “State of the Union,” referring to Mr. Navalny’s treatment.

Mr. Sullivan was vague when pressed on the timing of the sanctions or what they would include, saying only that additional action would come “as soon as we develop the packages to ensure that we’re getting the right targets.”

“When we do that,” he said, “we will impose further sanctions with respect to chemical weapons.”

In April, the Biden administration imposed its first sanctions on Russia for the poisoning and imprisonment of Mr. Navalny. But those penalties were not specifically directed at Mr. Putin or the oligarchs who support him.

Jen Psaki, the White House press secretary, said there was no significance to the timing of Mr. Sullivan’s remarks. “The law requires we keep looking at sanctions targets connected to chemical weapons use,” she said, noting that there had been “no change from before the summit to after the summit.”

Mr. Biden and Mr. Putin both described their three-hour meeting in Geneva on Wednesday as positive, even though few concrete actions came out of it other than an agreement to send ambassadors back to each other’s capitals.

After the meeting, Mr. Biden told reporters that he had been clear about consequences for Russia if Mr. Navalny, who was sentenced in February to more than two years in prison, were to die in captivity.

“I made it clear to him that I believe the consequences of that would be devastating for Russia,” Mr. Biden said.

“There has been no hostility,” Mr. Putin said in a separate news conference after the summit. “On the contrary, our meeting took place in a constructive spirit.”