U.S. listed tech stocks extended their slump in pre-market trading Tuesday, with each of the so-called FAANG names sliding into bear market territory after giving back nearly $1 trillion in value from their recent peaks amid persistent concerns over waning consumer demand, U.S.-China trade talks and rising interest rates.

Apple Inc. (AAPL) - Get Report and Nvidia Corp.  (NVDA) - Get Report probably best reflect two of those concerns, and thus have lead markets lower over the past week as investors question the depth of demand for Apple's new suite of iPhones, which were launched earlier this year, and what Nvidia CEO called a "hangover" of extra chips thanks to a fall-off in demand from cryptocurrency miners that has rippled across the semiconductor sector

"Trade war concerns with China weigh on the global supply chain for large technology companies while global growth fears worry many that future earnings will be lower," said Chris Zaccarelli, chief investment officer at the Independent Advisor Alliance. "Lastly, concerns that the Fed will keep raising interest rates causes price-to-earnings (P/E) ratios to contract as investors' calculations of current enterprise value drops as future cashflows are further discounted by higher interest rates."

"It's hard to know what will ultimately stop this decline, but I would expect it to be a resolution - or diminution - of some of the fears that are currently pushing the market lower," he added. 

Apple shares were marked 2.6% lower at the opening bell and changing hands at $181.00 each, a move that would takes the decline since its October 3 peak past 22% Nvidia shares fell 1% to 143.00 each, extending their near-term decline to 50%. 

Facebook Inc. (FB) - Get Report , which has fallen more than 40% since late July amid a host of data privacy, corporate governance and profitability concerns, was marked 1.5% lower $130.79 each. Alphabet (GOOGL) - Get Report slipped another 1.3% to $1,014.00, a move takes the Google parent more than 20% lower from its July 25 peak, while Amazon (AMZN) - Get Report was marked 3% lower at $1,465.00 each, extending its 3-month tumble past 27.5%.

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Facebook, Apple, Amazon, Alphabet and Netflix, the five core FANG names, had lost $945 billion in market value prior to today's open since each hit a 52-week high between July and October, with Amazon's $255 billion decline topping the list of lost value.  

The S&P 500 Information Technology subindex, the sector benchmark, has fallen some 13.5% since September but is still in modestly positive territory for the the year while the Philadelphia Semiconductor index, which tracks key chipmakers, is down nearly 6.4% on a year-to-date basis and has fallen 16.4% since September 1.