Venezuela exported more than 900,000 barrels per day (bpd) of oil last month, the third-highest monthly average so far this year, as PDVSA imported more naphtha to dilute its extra-heavy oil output. Even as Washington increased pressure on Maduro, Trump’s administration had not previously moved to interfere with oil flows.

The United States appears ready for war with Venezuela, a prospect that Venezuelan President Nicolás Maduro this weekend attributed to America’s desire to control the country’s vast oil reserves. Whatever the rationale behind the rapidly intensifying ...