"The Ukrainian leader also said that he and Trump had discussed the US proposal to take ownership of the Russian-occupied Zaporizhzhia nuclear power plant in south Ukraine. “We talked only about one power plant, which is under Russian occupation,” he said."The Ukrainians have attacked this powerplant so Russia has occupied it. Then the Ukrainians set some kind of fire - probably with drone(s) but it did not damage the plant. So it's not safe to give it back to Ukraine, and as long as the Russians hold control of it, the Ukraine would still target it. So having the US take control should mean that the Ukraine would not attack it if it's under US control, but they could use false flag techniques. At least this would give Ukraine a neutral party to control their power plant. And maybe the US is interested to know if Ukraine is producing weaponized nuclear fuel.
“Frank” is diplomatic phraseology that translates into disagreement between the two parties. No doubt, the US had to reiterate to the Ukrainians that they have no leverage and we are running the show.