Far-fetched as Mr. Trump’s vision for Gaza may be — the Arab world has roundly rejected it and any forcible removal of a population violates international law — it abruptly shifted attention away from the future of the cease-fire deal, whose initial, six-week phase is due to end in early March.

U.S. President Donald Trump said on Thursday that Israel would turn the Gaza Strip over to the United States after the fighting ends and that no U.S. soldiers would be needed there.