Iran has asked the International Court of Justice to order the United States to lift the sanctions, reimposed after US President Donald Trump pulled out of a multilateral 2015 accord.

Iran brought the case at the court in The Hague under a 1955 friendship treaty that predates the country's Islamic Revolution.

Washington told the court it had no jurisdiction to rule on the case, which it said was a matter of national security.

"Iran is not invoking the treaty of amity in good faith in this proceeding," US State Department lawyer Jennifer Newstead said in her closing argument.

"Iran cannot be permitted to draw this court into a political and psychological campaign" against the United States, she added.

During four days of hearings, Iran said the sanctions reintroduced this month are causing economic suffering for its citizens.

The US lawyers retorted that economic mismanagement was at the root of Iran's woes.

A second wave of US measures is due to hit Iran in early November, targeting its vital oil exports.

Closing the hearings, ICJ president Abdulqawi Yusuf said the court would issue a ruling "as soon as possible" but did not set a date.

"The judges are well aware of the political stakes," said Eric De Brabandere, professor of international dispute settlement at Leiden University in the Netherlands.

But "in principle the court will focus strictly on the legal aspects of the case", he told AFP.

Despite their 1955 Treaty of Amity and Economic Relations, Iran and the United States have not had diplomatic ties since 1980.

The ICJ was set up in 1946 to rule in disputes between countries.

The court is tasked with deciding only whether it has jurisdiction over Iran's request, De Brabandere said.

But he noted that "the political consequences of the decision are of course important," since either state would see a favourable outcome as "a huge victory".