Chinese Defence Ministry spokesman Wu Qian said on Thursday that China “resolutely” opposes U.S. deployment of intermediate range missiles in Asia, saying Washington is trying to “militarise” the South China Sea.

Wu said China will not sit back if the U.S. makes that move and urged it to take a responsible attitude and act with caution.

After the United States formally left the Intermediate-Range Nuclear Forces (INF) treaty with Russia in August, Defence Secretary Mark Esper said that he was in favour of placing ground-launched, intermediate-range missiles in Asia relatively soon.

If the U.S. deploys the missiles, it would severely harm the security interests of countries in the region and regional peace and stability, Wu said at a regular press conference.

The U.S. is attempting to “militarise” the South China Sea, he said.

The situation of the waters is stabilising at the current stage following China and other regional countries’ joint efforts, but the U.S. keeps provoking tension and “flexing muscles in the region,” he went on to say.

Speaking of U.S. Vice President Mike Pence’s recent criticism on China’s Belt & Road Initiative, Wu said China has reiterated the initiative is about economic connectivity, not geopolitics or military.