A second tanker dispatched by Iran was welcomed Monday by Venezuelan naval frigates and helicopters as it entered nationwide waters, a lifeline for embattled Venezuelan President Nicolás Maduro that reflects the closer ties being forged concerning Tehran and U.S. adversaries in Latin America.

The initial of five tankers carrying one.5 million barrels of gasoline, the Fortune, arrived in the predawn several hours at El Palito, a refinery in the vicinity of Puerto Cabello, in defiance of U.S. sanctions that largely prohibit oil investing with the gas-starved…