The United States vowed to fight Iran before the International Court of Justice (ICJ), calling Tehran’s move to question the legality of recently reimposed sanctions an attempt to interfere with its national security.

US Secretary of State Mike Pompeo issued the statement on Monday as legal proceedings began before the court in The Hague.

“Iran’s filing with the ICJ is an attempt to interfere with the sovereign rights of the United States to take lawful actions, including reimposition of sanctions, which are necessary to protect our national security. The proceedings instituted by Iran are a misuse of the court,” said Pompeo.

Iran has asked the international court to order the US to lift sanctions against Tehran after Washington unilaterally pulled out of the 2015 nuclear deal.

In the Netherlands on Monday, Mohsen Mohebi, the lawyer representing Iran, condemned the US for “naked economic aggression” in the first session of the case.

The measures have had “immediate damaging consequences on Iran and the Iranian people”, Mohebi said.

Iran said the US sanctions violate terms of a little-known 1955 friendship treaty between the two countries.