The Paris-based Financial Action Task Force (FATF) placed Iran on its terrorism financing blacklist after Tehran refused to comply with the watchdog's requirements.
The decision came after more than three years of warnings from the FATF, urging the Islamic Republic to either enact terrorist financing conventions or see its reprieve from the blacklist lifted and some counter-measures imposed.
"Until Iran implements the measures required to address the deficiencies identified with respect to countering terrorism-financing in the Action Plan, the FATF will remain concerned with the terrorist financing risk emanating from Iran and the threat this poses to the international financial system," the FATF said.
"FATF will remain concerned with the terrorist financing risk emanating from Iran and the threat this poses to the international financial system
Among the recommendations made, the FATF noted Iran should "adequately" criminalize terrorism financing and ratify United Nations antiterrorism financing conventions.
Although Iran's parliament passed the legislation, a top clerical body voted it down.
The blacklisting will complicate Iranian plans to sidestep American sanctions by instead doing business with European countries.
The governor of Central Bank of Iran (CBI) however said blacklisting Iran by the FATF will not be an issue for the country's foreign trade and stability of foreign currency market.
"During multiple periods of sanctions and maximum pressure, our monetary and financial system has become able to establish unsanctionable links with the world's monetary and financial system outside the framework of the FATF, and this has largely curbed the US' threats and hostility," Abdolnaser Hemmati wrote in an Instagram post.
Iran is alone with North Korea on a FATF blacklist, which severely restricts their access to loans and international aid. The agency has 37 nations and two regional organisations as members.