Iran told the United Nations’ highest court on Monday that Washington’s confiscation of some $2 billion in assets from Iranian state bank accounts to compensate bombing victims was an attempt to destabilize the Iranian government and a violation of international law.

In 2016, Tehran filed a suit at the International Court of Justice after the U.S. Supreme Court ruled money held in Iran’s central bank could be used to compensate the 241 victims of a 1983 bombing of a U.S. military base in Lebanon believed linked to Iran.

Hearings in the case opened Monday in the Hague-based court, starting with Iran’s arguments. The proceedings will continue with opening statements by Washington on Wednesday.

At stake are $1.75 billion in bonds, plus accumulated interest, belonging to the Iranian state but held in a Citibank account in New York.

In 1983, a suicide bomber in a truck loaded with military-grade explosives attacked U.S. Marine barracks in Beirut, killing 241 American troops and 58 French soldiers.

While Iran long has denied being involved, a U.S. District Court judge found Tehran responsible in 2003. That ruling said Iran’s ambassador to Syria at the time called “a member of the Iranian Revolutionary Guard and instructed him to instigate the Marine barracks bombing.”

The international court ruled it had jurisdiction to hear the case in 2019, rejecting an argument from the U.S. that its national security interests superseded the 1955 Treaty of Amity, which promised friendship and cooperation between the two countries.