President Donald Trump tweeted Thursday that he will add a new tariff on $300 billion of Chinese-made products on September 1, which would effectively put a tax on all Chinese goods coming into the United States.

“Trade talks are continuing, and during the talks the U.S. will start, on September 1st, putting a small additional tariff of 10 percent on the remaining 300 billion dollars of products coming from China into our country,” he tweeted.

Trade officials were in China this week to continue negotiations. In his tweets, the President called the talks “constructive,” but said the Chinese have not restarted buying American agricultural products as they had promised.

Last year, Trump imposed tariffs on about $250 billion in Chinese-made goods, targeting industrial materials and components. After a setback in negotiations in May, he announced that he would move forward with new tariffs on the remaining Chinese exports – but then said he’d put them off indefinitely.

The new tariffs could hit US consumers harder than the earlier rounds. It would tax goods like iPhones and other consumer electronics, sneakers, and toys.