China has asked Japan to work together in responding to the United States’ recent tariff moves. Chinese Premier Li Qiang sent a letter to Japan’s Prime Minister Shigeru Ishiba, urging a united stand against what he called “protectionist” policies by the US government.

The letter, sent through the Chinese embassy in Japan, was reported by Japan’s Kyodo news agency. It said China wants both countries to fight against unfair trade restrictions.

So far, the foreign ministries of both China and Japan have not made any official statements about the letter.

This appeal from China comes just one day after it warned other countries not to make trade deals with the US that could harm China’s interests. The tension continues to grow in the trade dispute between the US and China—the two largest economies in the world.

Japan, a strong ally of the United States, was also affected by the US tariffs introduced earlier this month. Japan has already started talks with the US to settle the issue.

Relations between China and Japan have been difficult in recent years due to several problems, including trade and territorial disagreements.