The US Coast Guard is readying new certifications to recognise shipowners for maintaining high safety and environmental standards. But only a few hundred ships may qualify for the designation.

The USCG said it plans to issue the first round of its "E-Zero" designation for ships that trade in US waters. E-Zero is part the USCG's Qualship 21 programme, which recognises ships from select flag states for having a three-year clean record for US detentions and violations.