The United States has criticized China for installing steel structures in the Yellow Sea, saying China’s refusal to abide by international law causes instability in the region.

A spokesperson for the U.S. State Department said Wednesday that China’s decadeslong refusal to abide by international law, including freedom of navigation, hampers its own economic interests and causes instability in the region. 

The department added that great powers are not afraid to state their intentions up front to contribute to stability that benefits all parties. 

According to the South Korean foreign ministry, China installed steel structures without due notice in the Provisional Maritime Zone in the Yellow Sea, an area where the two countries’ exclusive economic zones overlap. 

China defended the installations as aquaculture facilities amid concerns in South Korea that China could repurpose the structures for military use or use them as a basis for asserting territorial claims over the waters.

South Korea and China held a maritime cooperation dialogue in Seoul on Wednesday to discuss the issue.