WASHINGTON — A long-simmering trade conflict between the United States and Antigua and Barbuda appears to be boiling over.

Antigua and Barbuda, which has a $1 billion economy, is planning on getting legal retribution from the United States’ $15 trillion economy over its refusal to let Americans gamble at online sites based in the Caribbean nation — perhaps by offering downloads of American intellectual property, like Hollywood films, network television shows or hit pop songs. On Monday, the World Trade Organization gave its go-ahead for Antigua and Barbuda’s tentative plan.

“The economy of Antigua and Barbuda has been devastated by the United States government’s long campaign to prevent American consumers from gambling,” Harold Lovell, Antigua’s finance minister, said in a statement. “These aggressive efforts to shut down the remote gaming industry in Antigua have resulted in the loss of thousands of good-paying jobs and seizure by the Americans of billions of dollars belonging to gaming operators and their customers.”

The conflict’s roots are a decade old. The World Trade Organization said that the United States had violated its trade agreements by preventing Americans from betting at sites based in Antigua and Barbuda. Because Washington is unwilling to make the betting legal, the countries have been locked in a dispute over what constitutes fair trade practices and fair compensation.