The ruling by the International Court of Justice "once again shows that the US government... is day by day becoming more isolated," the foreign ministry said in a statement.

It said the court had found that the crippling sanctions reimposed by Washington after it abandoned a landmark 2015 nuclear deal between major powers and Tehran were illegal.

"World public opinion and all independent countries will, with peace of mind, strive... to keep and carry out the JCPOA," it added, using the official acronym for the agreement.

Foreign Minister Mohammad Javad Zarif called the court ruling "another failure for sanctions-addicted US government and victory for rule of law".

"Imperative for int'l community to collectively counter malign US unilateralism," he added in a tweet.