The Pentagon declined to comment and referred queries to the State Department.
Earlier, the Foreign Policy magazine reported, citing United States officials, that the administration of President Donald Trump is considering the possibility of cutting diplomatic personnel in Afghanistan and Iraq as soon as this year or the next.
The policy change has been rumored for years and in 2017, IRGC commander Mohammad Ali Jafari reportedly said if it was implemented, "then the Revolutionary Guards will consider the American army to be like Islamic State all around the world".
The new designation of the IRGC would allow the U.S.to act against companies and individuals who do business with the IRGC.
The decades-long conflict between Tehran and Washington reignited previous year when President Donald Trump unilaterally pulled the USA out of the Joint Comprehensive Plan of Action (JCPOA) on the Iranian nuclear program and re-imposed sanctions on the Islamic republic. They pledged to respond in kind against any action taken by the U.S. against Iran's armed forces.
Defense officials have told CNN that USA troops in Syria and Iraq often find themselves operating in close proximity to members of the IRGC.
Republican Senator Ben Sasse said the move would be an important step in America's maximum pressure campaign against Tehran.
Iran's most powerful security organisation, the IRGC was set up to protect the country's Shia clerical ruling system after its 1979 Islamic Revolution, which toppled the Western-allied secular monarch Shah Mohammad Reza Pahlavi and led to the formation of the Islamic Republic. Tehran has warned that it has missiles with a range of up to 2,000 km (1,242 miles), putting Israel and USA military bases in the region within reach.