The International Court of Justice (ICJ) has ordered the United States to pay compensation to Iranian companies after ruling that Washington had illegally allowed courts to freeze their assets.

The United Nations’ top court, also known as the World Court, did not specify the exact amount in its ruling on Thursday but said it would be determined in a later phase.

In a blow for Tehran, however, the tribunal in The Hague said it did not have jurisdiction over $1.75bn in frozen assets from Iran’s central bank held in a Citibank account in New York, by far the largest amount claimed back by Tehran.

ICJ Vice-President Kirill Gevorgian said the majority “upholds the objection to jurisdiction raised by the United States of America relating to the claims of the Islamic Republic of Iran” in regard to the bank.

The case was initially brought by Tehran against Washington in 2016 for allegedly breaching a 1955 friendship treaty.

In hearings last year, the US argued the case should be dismissed because Iran has “unclean hands” and the asset seizures were the result of its alleged sponsoring of “terrorism”. It added the money was to be given in compensation to victims of a 1983 bombing in Lebanon and other attacks linked to Iran.

The court on Thursday dismissed this defence entirely and ruled the treaty – signed long before Iran’s 1979 revolution – was valid.

The toppling of the US-backed shah and the establishment of the new government after the revolution severed US-Iranian relations, and Washington withdrew from the treaty in 2018.

Nonetheless, the ICJ ruled that it was still in place at the time of the freezing of the assets of Iranian commercial companies and entities, and that therefore Washington violated the treaty.

According to the judges, however, the court has no jurisdiction over the $1.75bn in assets held by the US because Iran’s central bank – known as the Bank Markazi – is not a commercial enterprise, and thus not protected by the treaty.

Iran said the court had demonstrated the legitimacy of its position and the “illegal” behaviour of the US.

“The verdict of the International Court of Justice handed down on March 30 shows once again the legitimacy” of Iran’s positions “and the illegal behaviour of the United States,” Tehran’s foreign ministry said in a statement.

The US said the ruling was a “major victory.”

“The court’s decision today rejected the vast majority of Iran’s case, including notably Iran’s claims on behalf of Bank Markazi,” said acting legal adviser Richard Visek of the US Department of State.

“This is a major victory for the United States and victims of Iran’s state-sponsored terrorism,” said Visek, who was at the reading of the verdict in The Hague.

The rulings of the ICJ are binding, but the court has no means of enforcing them. The US and Iran are among a handful of countries to have disregarded its decisions in the past.