China's countermeasures against the U.S. additional port fees on Chinese ships are "legitimate defense" actions aimed at maintaining a fair competition environment in the international shipping and shipbuilding markets, the Ministry of Commerce said Friday.

"The U.S. move is a typical unilateralist action of apparent discriminatory nature, which severely harms the interests of Chinese companies," a ministry spokesperson said in an online statement.

To safeguard the interests of domestic industries, Chinese authorities will charge special port fees on ships with U.S. affiliations, including those flying the U.S. flag, built in the United States, or owned, controlled, or operated by U.S. companies, in accordance with China's international maritime regulations, the spokesperson said.

These countermeasures are set to take effect simultaneously with the U.S. additional port fees on Chinese ships on Oct. 14. China urges the U.S. side to correct its wrongdoings and work with China to find a solution through equal-footed consultation and cooperation, the spokesperson added.