The test, Mr. Cutz said on Monday night, is whether the new sanctions prevent Russia and China from receiving Venezuelan oil as part of a debt repayment program. If so, he said, “that’s a pretty significant thing, and then the question is how Russia and China will respond, more than anything else.”

He said that Russia was close to being paid in full for its debt relief to Venezuela, but that China was on pace to be receiving oil from the South American country until early 2021. “They might stand to lose more,” said Mr. Cutz, who is now at the Wilson Center, a think tank in Washington.

Venezuela’s imports per capita have already fallen to the lowest level since the 1950s. The country’s imports totaled just $303 million in April, down 92 percent from the same month in 2012, according to Torino Capital.

Venezuela’s economy was already forecast to decline 35 percent this year, according to the International Monetary Fund. By the end of this year, the country’s gross domestic product will have shrunk by two-thirds since 2013, making it the largest economic collapse in a country outside of war since at least the 1970s.

The sanctions could also strain the lackluster political negotiations between Mr. Maduro and the country’s opposition, now based in Barbados and Norway, which many political analysts see as a final chance for a peaceful political transition in the country. Mr. Maduro’s negotiators have offered the opposition a prospect of presidential elections in return for the lifting of American sanctions — a possibility made more distant by the Trump administration’s action.

The order includes an exception for humanitarian goods such as food, clothing and medicine.

After Mr. Trump responded affirmatively to a reporter’s question last week about whether he was considering an embargo against Venezuela, an angry Mr. Maduro said on state television Friday that such a move would be “clearly illegal.” Mr. Maduro said he had asked Venezuela’s ambassador to the United Nations to protest the threat at the United Nations Security Council.

Trump officials have been frustrated by support for the Maduro government from Russia, China and Cuba, but have been able to do little to prevent it.

But Mr. Trump has happily embraced Venezuela’s socialist government as a political talking point, repeatedly citing its devastated economy as a cautionary tale of what he says Democrats would do if they were to win power in the United States. Mr. Trump’s Democratic critics say he has taken an unusual interest in the country mainly for that reason, and to impress Cuban and Venezuelan émigrés in the electorally crucial state of Florida.