The last big company doing classification work on Iranian ships, key to securing insurance and ports access, said on Friday it is stopping the work, spelling further difficulty for Iran's shipping, including its oil exports, Reuters reported.
The Korean Register of Shipping (KR) is the last of the world's top 13 classification societies to halt marine work in Iran following a recent exodus, including Britain's Lloyd's Register, triggered by Western sanctions on Tehran.
"In early August, the Korean Register of Shipping took the decision to stop providing classification services to Iranian ships. All relevant authorities and parties concerned were informed at that time," KR said in a statement on Friday.
"KR continues, at all times, to comply with all national and international regulations," it said, without further comment.
In July, KR had sidestepped calls by U.S. pressure group United Against Nuclear Iran to halt its verification work saying it was concerned that vessel safety and marine environment protection could be compromised.
Certification involves verifying safety and environmental standards and without it vessels have difficulty securing insurance cover and cannot call at most international ports.
Iran is under growing pressure over its disputed nuclear programme and companies are cutting ties with its shipping sector, which transports most of the OPEC member state's crude oil for fear of losing lucrative U.S. business.
"It's tightening the screws on them and while there are still options open to them, it restricts their ability to trade," said Richard Hurley, a shipping analyst with maritime intelligence publisher IHS Fairplay.
"The problem for Iran is they are increasingly being shut off in all directions and are increasingly falling back on their own resources."
While Western firms have pulled back from trading with Iran, a Chinese shipyard has delivered the first of 12 supertankers, giving Tehran extra capacity to transport its oil to Asia.
It is unclear if the vessel had classification cover.
The International Association of Classification Societies (IACS) classes more than 90 percent of the world's merchant fleet. It is made up of the top 13 of the more than 50 agencies that classify vessels.
IACS members such as Germany's Germanischer Lloyd and France's Bureau Veritas pulled out of Iran after being urged to exit by United Against Nuclear Iran, which includes former U.S. ambassadors on its board and is funded by private donations.
The pressure group backs tougher sanctions on Iran.
"We applaud KR for this responsible and significant decision," a spokesman for the group said on Friday.
"KR has joined other shipping services and countries in forcing Iran's business partners to now assume most all of the shipping risks for their business with the regime."