The rift over the war in Gaza between Israel and the United States, its closest ally, broadened on Sunday when Israel’s prime minister accused a top-ranking American lawmaker of treating his country like a “banana republic.”

Prime Minister Benjamin Netanyahu, who is facing increasing pressure to negotiate a cease-fire, lashed out at Senator Chuck Schumer over his call for elections to be held in Israel when the war winds down. In an interview on CNN’s “State of the Union,” Mr. Netanyahu suggested that Mr. Schumer, the Senate majority leader, was trying to topple his government and said his call for an election was “totally inappropriate.”