During a call with President Volodymyr Zelensky of Ukraine this week, President Trump floated a highly unusual idea: The United States could take control of Ukrainian nuclear power plants.

“The United States could be very helpful in running those plants with its electricity and utility expertise,” the White House said in a statement after the call on Wednesday. “American ownership of those plants would be the best protection for that infrastructure and support for Ukrainian energy infrastructure.”

The idea surprised officials and energy experts in Kyiv, and it was not clear whether Mr. Zelensky would agree to such a plan. Ukraine owns four nuclear power plants, and it also appears that the two sides do not agree on how many facilities the idea concerns.

Mr. Zelensky suggested at a news conference that the idea was limited to the Zaporizhzhia nuclear power plant, Europe’s largest, which is now under Russian control.

The Ukrainian leader described his discussions with Mr. Trump about the plant as “positive steps,” but added, “I’m not sure we will get a result quickly.”

The White House statement echoed a familiar argument from Mr. Trump: that U.S. economic involvement in Ukraine serves as its best security guarantee, because Russia would be less likely to target a country where America has economic interests. Mr. Trump has also applied such reasoning to a potential deal on access to Ukrainian critical minerals.