TEHRAN — Anger is building among even Iran’s staunchest defenders of the historic nuclear agreement with the United States, after a recent decision by the American Supreme Court allowing relatives of victims of a 1983 bombing to sue Tehran for $2 billion in compensation from frozen Iranian funds.


On Wednesday, President Hassan Rouhani, widely seen as the executor of the nuclear agreement, lashed out against the United States, calling the ruling a “continuation of hostilities against Iran” and a “flagrant theft and a legal disgrace,” the semiofficial Iranian Student News Agency reported.


The court ruled last week that the United States Congress did not exceed its constitutional role by enacting a law in 2012 making it easier for families of those killed in terrorist attacks to obtain compensation.


Iranian officials have repeatedly denied responsibility, however, and they accuse the United States of using the pretext of an attack to steal money that is rightfully theirs.


Mr. Rouhani called the Americans “thieves,” adding that they “imagine what they have pillaged belongs to themselves.”


The bickering over the Beirut bombing is the latest chapter in a series of disagreements and misunderstandings that have led to hard feelings since the euphoric days last summer after the signing of the nuclear deal between Iran and the major powers.


Iran was expecting a bonanza in unfrozen funds and new business opportunities after sanctions that had been imposed because of the nuclear program were lifted. But the continued presence of nonnuclear sanctions has slowed the process to a crawl, and foreign banks have been afraid to lend to Iranian companies because of potential penalties imposed by the United States.


So even though Iran has received a steady parade of business delegations from Europe and Asia, it has been unable to sign the big deals that might help revive its battered economy. Last week, Secretary of State John Kerry told a Jewish lobbying group in Washington that Iran to date had managed to retrieve only $3 billion of its frozen funds, from a total estimated at $55 billion to $100 billion.


Iran’s supreme leader, Ayatollah Ali Khamenei, added to the chorus on Wednesday, repeating his contention that the United States was deceitful and not to be trusted. While he had supported the nuclear deal, he always insisted that the United States would try to double-cross Iran.


The continuing financial restrictions are evidence of this, Ayatollah Khamenei hinted in a speech on his website, Khamenei.ir.


“America engages in tricks and practices deceit,” he said. “They write on paper that banks can cooperate with Iran, but in practice they promote Iranophobia so that no one trades with Iran.”


“American officials say that sanctions are still in place so that foreign investors get scared and do not come,” Ayatollah Khamenei said.


On Monday, Iran’s foreign minister, Mohammad Javad Zarif, who negotiated the nuclear deal, also strongly criticized the Supreme Court decision. “We hold the U.S. administration responsible for preservation of Iranian funds, and if they are plundered, we will lodge a complaint with the I.C.J. for reparation,” he said, referring to the International Court of Justice.


This article was written by Thomas Erdbrink for The New York Times on Apr. 27, 2016. Thomas Erdbrink, one of the few Western reporters accredited for U.S. media in the Islamic Republic of Iran, joined The Times in 2012 as Tehran bureau chief.