A dreadful week for technology stocks worsened on Monday as Amazon and Tesla shares fell further, setting a grim tone for markets already worried about China’s decision to raise import tariffs on U.S. products.

Amazon (AMZN.O) dropped as much as 3 percent after President Donald Trump launched his latest attack over the pricing of the world’s biggest online retailer’s deliveries through the U.S. postal system and promised unspecified changes.

The stock was the biggest drag on the S&P 500 .SPX and the Nasdaq .IXIC and weighed the most on the S&P consumer discretionary index .SPLRCD, which fell 1.32 percent.

The Facebook data scandal, self-driving car crashes and Trump’s intervention against Amazon pushed the S&P technology sector.SPLRCT to post its worst monthly losses in nearly two years in March.

Facebook (FB.O) was down 1.7 percent on Monday, while the other FANG constituents like Netflix (NFLX.O), Google-parent Alphabet (GOOGL.O) were down between 2 percent and 3 percent.

Tesla (TSLA.O) shares shed more than 5 percent ahead of the electric car maker’s announcement of quarterly production numbers for its crucial Model 3 sedan.

China, late on Sunday, said it would increase tariffs by up to 25 percent on 128 U.S. products, escalating a spat between the world’s biggest economies. The move came in response to U.S. duties on imports of aluminum and steel.

“That’s going to start stoking fears of trade wars and protectionism. The market doesn’t really like that,” said Andre Bakhos, managing director at New Vines Capital LLC in Bernardsville, New Jersey.

“And if it escalates, the questions could be on if China is going to buy our bonds. We have speculation out there, but it could be some profit taking and some risk-off mentality for the moment.”

Trump is separately preparing to impose tariffs of more than $50 billion targeting “largely high-technology” Chinese products.