WASHINGTON (AP) — President Donald Trump said Tuesday he is ordering a blockade of all “sanctioned oil tankers” into Venezuela, ramping up pressure on the country’s authoritarian leader Nicolás Maduro in a move that seemed designed to put a tighter chokehold on the South American country’s economy.

Trump’s escalation comes after U.S. forces last week seized an oil tanker off Venezuela’s coast, an unusual move that followed a buildup of military forces in the region. In a post on social media Tuesday night announcing the blockade, Trump alleged Venezuela was using oil to fund drug trafficking and other crimes and vowed to continue the military buildup until the country gave the U.S. oil, land and assets, though it was not clear why he felt the U.S. had a claim.

“Venezuela is completely surrounded by the largest Armada ever assembled in the History of South America,” Trump said in a post on his social media platform. “It will only get bigger, and the shock to them will be like nothing they have ever seen before — Until such time as they return to the United States of America all of the Oil, Land, and other Assets that they previously stole from us.”