The story: The apparent understanding between Iran and the US to de-escalate tensions is experiencing both challenges and progress, highlighting the fragility of the process.

Tehran and Washington reportedly have an "informal arrangement" in place that permits the flow of Iranian oil into the market. Following the recent Iran-US deal to swap prisoners and unfreeze some Iranian assets abroad, claims have also emerged that Tehran has slowed down its accumulation of highly enriched uranium.

Yet the Islamic Republic has lashed out at the US over the reported seizure of Iranian oil. The potential sale of the...