Washington (CNN) The parents of Otto Warmbier filed a claim for a North Korean cargo ship that was seized by the US in May, noting the asset could be used to pay off part of the family's $500 million judgment against the country.

In December, a federal judge awarded the Warmbier family more than half a billion dollars in a wrongful death suit against the North Korean government.

North Korea never engaged in settlement discussions, according to the new filing, "Hence, the Warmbiers are left to chase down the assets of North Korea to recover what they can for the torture and death of their son at the hands of North Korea's dictator, who with "his cronies, show(s) no regard for human life.""

"We are committed to holding North Korea accountable for the death of our son Otto, and will work tirelessly to seize North Korean assets wherever they may be found," Fred and Cindy Warmbier said in a statement.

The seized ship was used to transport coal from North Korea that was sold in other countries, including China, the Justice Department said in May. The US and the United Nations have said that North Korea has used illicit sales of its coal to fund the country's nuclear weapons and ballistic missiles program.

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