Seoul is seeking an exemption from a European Union embargo that would effectively halt shipments of Iranian oil to South Korea from July 1, officials said on Tuesday.
The EU decided in January to enforce a full embargo on Iranian crude as part of efforts to bring Tehran back to international talks over its suspected nuclear weapons programme.
It will also ban European firms from insuring or reinsuring tankers transporting Iranian oil anywhere in the world -- a move that could mean Korean refiners are unable to import supplies.
South Korea and Japan have been asking the EU for an exemption from the insurance ban, said Jung Jong-Yung, a director of the Ministry of Knowledge Economy.
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Another government official told Dow Jones Newswires it was "very difficult" to find an alternative supply source in a short period. Iran currently supplies about 10 percent of South Korea's crude imports.
Seoul is "doing its best" to secure an exemption from US sanctions on Iran, and from the European insurance ban, the official said.
The EU is likely to decide next month after Seoul's request, the official added.
SK Energy and Hyundai Oilbank, the two Korean companies that import Iranian crude, said they had been consulting closely with government authorities to seek a South Korean exemption from the insurance ban.
"The government is seeking to earn time until December at least," a Hyundai Oil spokeswoman said. "We're crossing our fingers and hope the negotiations with the EU turn out to be fruitful."