South Korea's government said Tuesday that talks with the EU to extend insurance of South Korean tankers that ship Iranian oil had failed.
South Korea relies on European insurance companies to insure its oil tankers.
EU firms will be banned from insuring tankers carrying Iranian oil from July 1.
South Korea is one of the four major Asian buyers of Iranian oil along with China, Japan and India.
South Korea imported 87 million barrels of crude oil from Iran in 2011. Iran accounted for 9.4 percent of South Korea's total crude oil imports.