The decision concerned compensation claims by more than 1,000 Americans — survivors and relatives of people killed in attacks that the American authorities have attributed to Iranian operatives — despite Iran’s denials of responsibility. The attacks include the 1983 truck bombing of a Marine base in Beirut, Lebanon, and a 1996 truck bombing in Khobar, Saudi Arabia.

Iran had previously called the Supreme Court decision a form of theft and had suggested it might sue the United States in the International Court of Justice to block the ruling from taking effect. But Thursday appeared to be the first time Iran suggested it might be planning a reciprocal response.

“The entire court proceedings which led to the recent ruling has been fake and phony and a travesty of justice in every sense of law, jurisdiction, merit, fact and process,” the foreign minister, Mohammad Javad Zarif, wrote in the letter to Secretary General Ban Ki-moon, which was released by Iran’s United Nations Mission.