By Twesha Dikshit and Purvi Agarwal

(Reuters) -Wall Street's main indexes fell to near two-week lows on Thursday, as technology stocks came under fresh selling pressure, while U.S. tariff concerns and uncertainty around the health of the economy kept investors on edge.

Most tech stocks declined as worries over stretched valuations resurfaced, after a brief respite on Wednesday. Warnings of a market pullback from Wall Street executives on Tuesday had prompted a sharp equity sell-off led by AI-linked stocks.

Heavyweights Microsoft and Nvidia lost 1.8% and 3%, respectively, weighing on the information technology sector. The broader semiconductor index was down 2.4%.

Qualcomm dipped 4.9% after the chip designer warned of a possible loss of business next year from its key customer, Samsung, but issued an upbeat forecast.

DoorDash slumped 16.5% to the bottom of the S&P 500 after the delivery firm reported third-quarter profit below Wall Street expectations, while Tapestry lost 10.7% after forecasting holiday-quarter earnings below expectations.

The stocks weighed on the consumer discretionary sector, which fell 2.7%.

Tesla fell 4.5%, ahead of a shareholders' vote, where they will decide on CEO Elon Musk's heavy compensation among other proposals.

"We have uncertainty from the Fed decision next month, on where the tariffs are going, with the government shutdown... the markets are a little bit cautious right now," said Dennis Dick, chief strategist at Stock Trader Network.

"It's been an excellent couple of months for the market and a little bit of a corrective phase here is warranted."

At 12:02 p.m. ET, the Dow Jones Industrial Average fell 490.10 points, or 1.04%, to 46,820.90, the S&P 500 lost 76.72 points, or 1.13%, to 6,719.71 and the Nasdaq Composite lost 424.46 points, or 1.81%, to 23,075.34.

The longest U.S. government shutdown in history has led to investors and the Federal Reserve to rely on mixed private sector indicators ahead of December's monetary policy meeting.

Global outplacement company Challenger, Gray & Christmas said on Thursday layoffs announced by U.S. employers surged in October, marking the highest level for the month in 22 years, while data from Revelio Labs showed the economy shed jobs last month.

An estimate by the Chicago Fed showed U.S. jobless rate likely edged up in October to the highest in four years.

The datasets were in contrast to Wednesday's strong ADP report, spurring uncertainty over the health of the U.S. labor market.

Chicago Fed President Austan Goolsbee also reiterated his cautious stance on further rate cuts in the absence of official data. Comments from other Fed officials will also be parsed through the day.

Investors assessed a bag of mixed corporate earnings. Datadog topped the S&P 500 with a 22.2% surge after the cloud security firm raised its annual profit and revenue forecasts.

Robinhood dropped 8.9% after the online brokerage raised its forecast for fiscal-year operating expenses.

Drugmakers Eli Lilly and Novo Nordisk ( NVO ) unveiled a deal to slash the prices of popular GLP-1 weight-loss drugs for the government's Medicare and Medicaid programs, and for cash payers.

Eli Lilly ( LLY ) extended gains to trade 1.8% higher, while U.S.-listed shares of Novo Nordisk ( NVO ) were flat in choppy trading.

Among others, DraftKings was up 8.9% after a Bloomberg News report that Disney signed the company as ESPN's new sports-betting partner.

Declining issues outnumbered advancers by a 2.01-to-1 ratio on the NYSE and by a 2.77-to-1 ratio on the Nasdaq.

The S&P 500 posted 16 new 52-week highs and 20 new lows while the Nasdaq Composite recorded 70 new highs and 190 new lows.