Though Venezuelan generals appear to be backing Mr. Maduro, a handful of Venezuelan diplomats and officials posted to missions in the United States have said they are abandoning the Maduro government to support Mr. Guaidó. On Monday, Scarlett Salazar, a veteran diplomat based in Miami, where there is a large anti-Maduro Venezuelan population, announced she was siding with Mr. Guaidó.

Most Latin American countries have recognized Mr. Guaidó and demanded that Mr. Maduro acquiesce to the call for new elections. Several European nations also joined the call for elections after Mr. Pompeo held a meeting with representatives of the United Nations Security Council in New York on Saturday.

The campaign by the Trump administration has gotten a high level of bipartisan support among lawmakers in Washington, though some Democratic legislators have expressed concern about how hard-line policies might affect ordinary Venezuelans, who are already suffering from years of economic collapse. Others have asked whether the administration has a coherent strategy if Mr. Maduro clings to power.

On Monday, the United States put into effect what is essentially an embargo on oil from the main Venezuelan state-owned oil company, Petróleos de Venezuela, or Pdvsa. The sanctions would prevent most American companies from doing business with Pdvsa. Any money going to Pdvsa — including from its United States subsidiary, Citgo — would be put into accounts that could be used by what the Trump administration deems to be the legitimate Venezuelan government. For now, that is Mr. Guaidó and the National Assembly, where the 35-year-old political activist and industrial engineer serves as leader.

The oil sanctions amount to the first punitive action taken by the United States against Mr. Maduro since the power struggle in Caracas erupted last week, and it is intended to starve the government of Mr. Maduro of cash and foreign currency. Oil production in Venezuela has already plummeted because of mismanagement and poor policies, and the country’s economy is in shambles. Extraction at oil fields still takes place, though, and until now the country exported much of its crude oil to the United States to be refined and then sold.