President Trump on Saturday demanded China “end unfair trade” amid his escalating beef with the country over trade tariffs.

“The United States hasn’t had a Trade Surplus with China in 40 years,” Trump tweeted Saturday afternoon. “They must end unfair trade, take down barriers and charge only Reciprocal Tariffs. The U.S. is losing $500 Billion a year, and has been losing Billions of Dollars for decades. Cannot continue!”

On Thursday, Trump threatened an additional $100 billion in tariffs on Chinese imports “in light of China’s unfair retaliation” against the $50 billion in duties he proposed earlier this week. China had responded by outlining $50 billion in American products that would get tariffs.

A Chinese official on Friday responded to the new threat by saying the nation “is fully prepared to hit back forcefully and without hesitation.”