In the wake of a disastrous fall in stocks following economic news, US President Donald Trump announced Friday evening that tariffs on Chinese imports would be stiffened even more.

Trump made the announcement Friday evening via Twitter, about an hour after the New York Stock Exchange closed for the day. The Dow Jones Industrial Average had already collapsed 623 points by the closing bell.

"For many years China (and many other countries) has been taking advantage of the United States on Trade, Intellectual Property Theft, and much more," Trump tweeted. "Our Country has been losing HUNDREDS OF BILLIONS OF DOLLARS a year to China, with no end in sight. Sadly, past Administrations have allowed China to get so far ahead of Fair and Balanced Trade that it has become a great burden to the American Taxpayer."

"As President, I can no longer allow this to happen! In the spirit of achieving Fair Trade, we must Balance this very unfair Trading Relationship. China should not have put new Tariffs on 75 BILLION DOLLARS of United States product (politically motivated!). Starting on October 1st, the 250 BILLION DOLLARS of goods and products from China, currently being taxed at 25%, will be taxed at 30%. Additionally, the remaining 300 BILLION DOLLARS of goods and products from China, that was being taxed from September 1st at 10%, will now be taxed at 15%."

"Thank you for your attention to this matter!"​ the president wrote.

The Office of the US Trade Representative (USTR) issued a statementFriday following the president's comments, noting that "a notice and comment period" will precede the imposition of the new tariffs.

​Trump's announcement follows his tumultuous comments about trade with China earlier in the day that sent markets into a tailspin.

"We don’t need China and, frankly, would be far better off without them,” Trump raged on Twitter after the Tariff Committee of the State Council of the People's Republic of China announced retaliatory tariffs on $75 billion worth of imported US goods, as well as suspended trade penalties on US automobiles and their parts, all of which would enter force before the end of the year.

That, in turn, was just the latest tit-for-tat in the trade war that's been steadily accelerating since last summer. At the start of the month, Trump announced a 10% tariff on $300 billion worth of Chinese imports that would take effect on September 1, although he later postponed that to the end of the year, ostensibly because of the Christmas buying season in the US.

The Dow, already unsteady, plunged by 767 points that day and would fall by hundreds more points on several occasions in subsequent weeks. By mid-month, US stocks had lost 7% of their value, and key economic indicators suggested a recession was on the horizon.

Trump, however, remained adamant as ever about the strength of the US economy, an optimism echoed in Friday's declaration.