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April 16 (Reuters) - Wall Street index futures dropped on Wednesday and chip darling Nvidia slumped after the company flagged steep charges from new U.S. curbs on chip exports to China, fuelling worries about the fallout of an escalating trade war.

The U.S. Commerce Department late Tuesday issued new export licensing requirements for Nvidia's NVDA.O H20, and AMD's AMD.O MI308 artificial intelligence chips to China.

Nvidia NVDA.O said it faces $5.5 billion in charges after the curbs on exports to China, a key market for one of its most popular chips.

Shares of the heavyweight stock slumped 5.2% in premarket trading, while AMD shares lost 5.9%. Other chip stocks too lost ground, with Micron Technology MU.O down 3.5% and Broadcom AVGO.O falling 3.1%.

Futures for Wall Street's main indexes fell across the board, with those tracking the tech-heavy Nasdaq 100 NQcv1 leading the declines.

The new export controls are the newest attempt from the U.S. to keep advanced semiconductors from being sold to China, and the latest escalation of trade tensions between the world's two largest economies.

Nvidia's warning highlighted the impact of the escalations on businesses, and re-fueled worries that the constant shifts in U.S. trade policy would hit consumption and economic growth.

Those worries have led to sharp volatility in financial markets, with all three major Wall Street indexes losing ground so far this year.

The CBOE volatility index .VIX, Wall Street's "fear gauge," ticked up to 31.86 after falling for the past three sessions.

Separately, U.S. President Donald Trump ordered a probe into potential new tariffs on all U.S. critical minerals imports.

At 5:00 a.m. ET, Dow E-minis 1YMcv1 were down 80 points, or 0.18%, S&P 500 E-minis EScv1 were down 34.75 points, or 0.64% and Nasdaq 100 E-minis NQcv1 were down 227.5 points, or 1.2%.

Given the market volatility and growth worries sparked by trade uncertainty, investors will closely monitor a speech by Federal Reserve Chair Jerome Powell later in the day for indications on how the central bank could respond.

Traders see a 20% chance that the Fed will ease rates by 25 basis points at its May meeting, as per CME FedWatch.

March retail sales, due at 8:30 a.m. ET, will also be scrutinized for clues on how consumers are faring amid uncertainty and rising inflation expectations.

Corporate results are also in focus. Shares of United Airlines UAL.O rose 6.2% after the company reported stable bookings, despite forecasting lower profit for the current quarter, and flagging risks if the U.S. economy slips into recession.

(Reporting by Lisa Mattackal in Bengaluru; Editing by Shinjini Ganguli)

((LisaPauline.Mattackal@thomsonreuters.com;))