Iran thought its Grace 1 tanker, renamed the Adrian Darya-1, had evaded the US and escaped from Gibraltar en route to Syria. But Greece refused to facilitate the course of the ship to Syria on Wednesday.

The US is putting pressure on countries not to aid the ship. Washington alleges that the ship is linked to the Iranian revolutionary Guard Corps, which it views as a terrorist organization. Tehran thinks that the release of the ship is a blow to the US. In early July, Britain's Royal Marines had seized it, but Iran seized a British tanker in response and Gibraltar allowed the Iranian ship to continue on its way this week.
The US, however, has upped rhetoric against Iranian tankers and shipping. It now appears this will be a central part of the new American “maximum pressure” campaign against Iran. The Adrian Darya will now be a test case for other tankers alleged to be moving Iranian oil, including those going to Syria.
It may become increasingly difficult for Iran in these circumstances, which will lead to more tensions in the Persian Gulf and could result in a new round of crises and threats between Tehran and Washington.
Reports that a US drone was shot down in Yemen and of Iran unveiling a new air defense system seem timed to threaten the US by showing that the Islamic Republic can still strike at American assets elsewhere.