CARACAS, Venezuela — The Trump administration announced sanctions against Venezuela’s vice president on Monday, calling him a drug “kingpin” in its first moves against the country’s leftist government, which President Trump railed against during his campaign.

Vice President Tareck El Aissami, according to a Treasury Department statement, was being sanctioned for “playing a significant role in international narcotics trafficking.” The sanctions mean that Mr. El Aissami, 42, will be blocked from financial dealings with Americans and will have any American assets frozen.

Such actions against officials in the government of President Nicolás Maduro of Venezuela are nothing new in a long and fraught relationship between Washington and Caracas. But the accusation that Mr. El Aissami, the next in line for the presidency, is a drug trafficker is certain to set a new, more hostile tone in relations.

“This can be seen as the opening salvo of the Trump administration in dealing with Latin America’s deepest crisis,” said Michael Shifter, the president of the Inter-American Dialogue, a policy group in Washington. “It is hard to imagine that, with this decision, Washington will now be inclined to offer many carrots to the increasingly authoritarian regime.”