There was optimism when the United States and Iran signed a memorandum of understanding (MOU) on 17 June, intended to end the US-Israel-Iran war that began on 28 February and to establish a 60-day negotiating period leading to a final agreement on Iran's nuclear programme.
But the 14-point document was hastily put together and includes nebulous articles open to interpretation.
Disagreements over Article 5 - which concerns shipping traffic in the Strait of Hormuz - have caused skirmishes and led ultimately to last week's major escalation.
Article 5 calls on Iran to "make arrangements ... for the safe passage of commercial vessels" in the Strait of Hormuz during the 60-day negotiating window.
Iran has interpreted the article as giving it the right to direct traffic, including instructing ships to take only those routes it has approved as safe. The US understands the article as meaning that Iran is obliged to reopen the strait fully and unconditionally.
