The United States and other Western nations have targeted Iran's energy sector for sanctions as an effort to cut off revenues it believes Iran is using to build nuclear weapons. Tehran has insisted its program is for civilian purposes.
The European Union is poised to ban imports of Iranian gas, a measure it may formally adopt at a meeting of foreign ministers on Oct. 15.
"The (EIA) report gives cover for the administration to broaden sanctions to cover natural gas exports," said Mark Dubowitz, the head of the Foundation for Defense of Democracies, an advocate for stronger sanctions on Iran.
Iran has large reserves of natural gas, but its current exports go mainly to Turkey, which buys more than 90 percent of the output under long term contracts. Armenia and Azerbaijan purchase 6 percent and 3 percent, respectively.
"Clearly, Turkey would be placed in a very difficult position in the event that it is unable to continue importing Iranian natural gas," the EIA said.
A prolonged period without access to Iran's natural gas could "have a major disruptive effect" on Turkish industry, home heating and power generation, the report said.
Congress is also considering tweaks to a U.S. sanctions law that could blacklist a broader range of Iran's energy sector.