The flare-up in trade tensions sent global equities to the steepest losses of the year, wiping more than $1 trillion from stock values around the world Monday.

The MSCI All-Country World Index fell 2% as of 12:55 p.m. in New York, headed for the worst day since early December. Selling was heaviest in the U.S., where the S&P 500 Index plunged 2.5% and the Nasdaq Composite tumbled more than 3%. European shares lost 1.2% and emerging-market stocks slid 1.7%.

Trade tensions have sent U.S. stocks lower in five of the past six sessions. Selling intensified Monday after China defied the Trump administration’s warning not to retaliate for his imposition of higher tariffs Friday, driving demand for havens from gold to the yen while punishing risk assets.