US threats are stymying Iranian efforts to attract upstream investment. But European and Asian buying of Iranian crude will likely be unaffected.

Iran’s economy is being buffeted by geopolitical winds which threaten to derail President Hassan Rohani’s second term.

Heightened expectations that US President Donald Trump may opt to pull his country out of the Iran nuclear accords have contributed to a renewed devaluation of the Iranian Rial, which has sunk to record depths.

As...