The first of what is expected to be five Iranian oil tankers has docked at a Venezuelan refinery, defying U.S. sanctions on both countries.
The ship arrived in Venezuela Sunday and the country's oil minister announced that it has moored at the El Palito refinery.
A second ship entered Venezuelan waters Monday and a third is sailing through the Caribbean.
"I want to thank - from the most noble and sensible heart of the Venezuelan people - the Islamic Republic of Iran, President Rouhani, my friend and colleague, Supreme Leader Ayatollah Khamenei ... and all of Iran, from the heart, for its solidarity, for its support," President Nicolas Maduro said.
Despite its oil wealth, Venezuela is experiencing severe fuel shortages. The collapse of its economy along with U.S. sanctions has nearly destroyed its refining capabilities.
Iran has agreed to send more than one and a half million barrels of gasoline and parts to Venezuela.
Neither the White House nor State Department had any comment Monday. But a top Trump official said last week the U.S. is considering how to respond.
U.S. sanctions forbid Iran from selling oil and has also imposed sanctions on the Venezuelan economy, including its state-run oil company, as part of an effort to drive Maduro from power.