Iran has gone to the United Nations' highest court in a bid to have the US sanctions against it lifted.
Iran filed a case with the International Court of Justice in July, saying the sanctions imposed by the Trump administration violate the terms of a little-known 1955 friendship treaty between the two countries. The Treaty of Amity regulates economic and consular ties between Iran and the US.
On Monday, Iranian lawyers will ask the court to order the United States to lift the sanctions., which have further damaged Iran's already weak economy.
The United States, which will respond formally in oral arguments on Tuesday, has yet to issue a public response.
US lawyers are expected to argue that the UN court does not have jurisdiction in the dispute, that the 1955 treaty is no longer valid, and that in any case the sanctions do not violate it.
The hearings, essentially a request by Iran for a provisional ruling, will last for four days, with a decision to follow within a month.
The ICJ is the UN tribunal for resolving international disputes and its rulings are binding, but it has no power to enforce them and on rare occasions they have been ignored by some countries, including the United States.
In May, US President Donald Trump pulled out of the 2015 nuclear pact between Iran and the five permanent members of the UN Security Council. The 2015 deal aimed to have Iran rein in its nuclear program in exchange for the lifting of crippling international sanctions.
Earlier this month, the US reimposed the first of two waves of sanctions on Iran. The second set is expected to be enacted in November.
Although the US's European allies have protested against Trump's move, most Western companies intend to adhere to the sanctions, preferring to lose business in Iran than to be punished by the United States or barred from doing business there.
The ICJ has so far ruled that the 1955 treaty is still valid, even though it was signed long before the 1979 Islamic Revolution that triggered decades of hostile relations with the US.
