WASHINGTON — The Trump administration imposed sanctions against Venezuela’s state-owned oil company on Monday, seeking to cripple the government of embattled President Nicolás Maduro by cutting off its main source of cash.

The move marked the first punitive step by the United States to force Mr. Maduro to give up power since the opposition leader, Juan Guaidó, declared himself interim president last week after years of accusations of corruption in Venezuela at the expense of its people.

The sanctions prohibit most American businesses from engaging in transactions with the oil company, Petróleos de Venezuela, S.A., or Pdvsa. Administration officials said the financial penalties are expected to block $7 billion in assets and result in $11 billion in export losses over the next year for Venezuela’s government, starving it from its most important source of revenue and foreign currency.

Last week, the Trump administration recognized Mr. Guaidó, the 35-year-old leader of the National Assembly, as his supporters took to the streets to demand new elections. Mr. Maduro has cut ties to the United States and has demanded that all American diplomats leave the country.