Speaking in Ankara, President Recep Tayyip Erdogan said it goes against the independence of states to cut ties with its "neighbor and strategic partner" because the U.S. demands it.
President Donald Trump announced in May that he would pull out of a 2015 agreement over Iran's nuclear program and would re-impose sanctions. His administration threatened countries with sanctions if they don't cut off Iranian oil imports by early November.
Turkey imported 3 million tons of crude oil from Iran in the first four months of 2018, amounting to 55 percent of crude supplies and 27 percent of its total energy imports.
Erdogan asked Wednesday: "Who will heat my country throughout the winter?"