A United Nations tribunal on Wednesday ordered that the US suspend sanctions on humanitarian trade and civil aviation with Iran, a decision that Tehran called victory in its fight against the Trump administration.
It is not clear whether Washington will comply with the ruling of the International Court of Justice, which would make it more difficult to increase its economic pressure against Iran.
Washington argues that the court has no jurisdiction over its sanctions. There was no immediate statement from the State Department.
The Wednesday decision was a preliminary injunction on a wider case in which Iran questioned the legality of US sanctions. This major case could take years to resolve.
While Washington has said its sanctions are not aimed at humanitarian aid, the ruling could undermine its sanctioning strategy if implemented.
Following US President Trump's decision in May to pull the US out of Iran's 2015 nuclear deal, Washington is reinstating sweeping sanctions against Tehran.
The court said that the payment channels needed to carry out humanitarian and air traffic should be available, which means that the financial sanctions of the United States may need to relax. The US threat to deny foreign companies and banks access to the dollar market and the US financial system is the key financial instrument that has enabled Washington to reduce international trade with US enemies such as Iran and North Korea.
The ruling would also require that the US suspend the revocation of licenses for the sale of commercial aircraft and parts to Iran. This move was part of a first round of new sanctions that came into force in August.
The court said the US should take no further steps to tighten the conflict, which could mean that no further financial and energy sanctions are planned by Washington in November.
These measures, which foreign companies can use to sanction trade with Iran, have resulted in many large foreign companies leaving Iran and breaking economic ties.
In its ruling, the ICJ said that the new financial and economic sanctions already damaged humanitarian trade with Iran and restricted trade in aircraft and spare parts.
The decisions of the ICJ are theoretically binding, but the court has no means to enforce them. The court decides on disputes between U.N. members.
Trump officials have turned down other international courts, with national security adviser John Bolton, who is recently threatened with sanctions against international criminal court judges, prosecuting charges against US citizens.
Iranian Foreign Minister Javad Zarif tweeted that the verdict was a "victory for the rule of law" and called on the international community to "jointly fight the evil US unilateralism".
Iran's claim to the court rests on a 1955 US-Iran bilateral agreement that was committed to maintaining economic relations. Diplomatic relations between Washington and Tehran were broken off after the Iranian revolution of 1979, but the treaty was not abrogated.
Iran had asked the court for a preliminary decision to suspend US action prior to the full reintroduction of US sanctions next month.
Washington says its restrictions are allowed in the 1955 treaty in national security cases.
For Tehran, the case was a way to demonstrate at home the international position of the 2015 nuclear agreement, while he built his case that Washington's withdrawal from the agreement isolated the United States.
The nuclear agreement is supported by Europe, Russia and China. These countries are trying to maintain some of the economic benefits of the agreement for Iran in the face of escalating US sanctions.
The agreement lifted most international sanctions against Iran for strict but temporary restrictions on Tehran's nuclear program.
-Asa Fitch contributed to this article.
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