IN DEFIANCE of the vast majority of its own people, the Venezuelan government is pressing ahead with a plan to dismantle what remains of the country’s democratic political institutions. This Sunday it intends to stage a rigged vote to create a constituent assembly that would have the power to overrule all other bodies, including the elected National Assembly, state governors and courts. Though President Nicolás Maduro and the corrupt clique around him have been vague about their ultimate intentions, it’s probable the constituent assembly will be used to abolish the opposition-controlled legislature, cancel future elections and establish a regime resembling that of Cuba’s.

Months of daily street demonstrations by hundreds of thousands of Venezuelans, in which more than 100 people have died and more than 1,000 have been injured, have done nothing to stop the regime’s drive toward dictatorship. Last week, more than 7 million people opposed the constituent assembly in an opposition-organized referendum — or 2 million more than supported the government in the last election. The regime shrugged. Nor has it heeded appeals from its Latin American neighbors and other Western democracies.

Attempts to broker a deal between the government and the opposition by friendly socialist statesmen and the Vatican have failed, because Mr. Maduro and his associates, deeply involved in drug trafficking and massive theft, have no interest in compromise. A general strike and plans for another mass demonstration in Caracas on Friday are the opposition’s last-ditch attempts to stop what can only be called a coup.

As a once-prosperous oil-producing nation has descended into political chaos and humanitarian crisis over the past several years, the response of the United States and other democracies has been consistently inadequate — “too little and too late,” as Luis Almagro, the secretary general of the Organization of American States, put it. A turning point was passed last year when the Obama administration, rather than insist that the regime respect a constitutional process for a recall election, instead pressured the opposition to participate in fruitless negotiations.

To its credit, the Trump administration has toughened U.S. policy, decreeing three rounds of sanctions on senior Venezuelan officials involved in drug trafficking and the suppression of democracy; 13 more people were named on Wednesday. President Trump issued a statement last week promising “strong and swift economic actions” if the constituent assembly election goes forward.

The risk now is that U.S. policy will go too far. The White House is reportedly considering sanctions on Venezuelan oil exports, which provide 95 percent of the country’s export revenues, including a possible ban on the approximately 700,000 barrels a day that go to the United States. That action would be devastating to Venezuela’s 30 million people, who already face dire shortages of food and medicine. It will also give the Maduro regime an excuse for the catastrophic economic conditions it has created — and for which it now bears exclusive blame.

If the constituent assembly is called, the United States should react decisively — but it should do so in ways that punish Venezuela’s corrupt rulers, not its long-suffering population.