Shares of Intel Corp tumbled 16%, weighing the most on all three indexes after the company said it was six months behind schedule in developing next-generation, power-efficient chip technology and that it would consider farming out more work to outside semiconductor foundries.
Rival Advanced Micro Devices Inc gained 14.6%, but the broader Philadelphia semiconductor index dropped 1.1%.
Shares of U.S. drugmakers fell ahead of executive orders by President Donald Trump aimed at lowering drug prices.
The healthcare index shed 1.4%.
The S&P 500 and the Dow are set to clock in their first weekly decline in four as investors feared that the COVID-19 health crisis that has spiraled in recent weeks and has infected over 4 million Americans, could hamper a recovery in economic activity.
Optimism about a potential coronavirus vaccine and fiscal stimulus package had helped the benchmark S&P 500 hit a five-month high earlier this week.
"U.S. equities are in consolidation mode for a good reason. We've seen a strong performance in the last three months," said Terry Sandven, chief equity strategist at U.S. Bank Wealth Management in Minneapolis, Minnesota.
"When you look further into the second half of the year, there's reason to expect some volatility in the broad market ... the duration and impact of COVID-19 is still unknown."
Latest survey showed U.S. business activity increased to a six-month high in July, but companies reported a drop in new orders as a resurgence in new COVID-19 cases weighed on demand.
Sentiment took a hit earlier in the day after Beijing ordered Washington to close its consulate in the city of Chengdu, days after U.S. ordered the closure of the Chinese consulate in Houston.
At 12:43 p.m. ET, the Dow Jones Industrial Average was down 159.53 points, or 0.60%, at 26,492.80 and the S&P 500 was down 24.03 points, or 0.74%, at 3,211.63. The Nasdaq Composite was down 118.90 points, or 1.14%, at 10,342.51.
Of the 113 S&P 500 companies that have reported quarterly results, 80.5% of them have beaten dramatically lowered profit estimates, according to IBES Refinitiv data.
Oilfield services giant Schlumberger NV dropped 1.6% as it outlined plans for deeper spending cuts after recording a $3.7 billion charge and a second straight quarterly loss.
American Express Co slipped 0.2% after it reported an 85% slump in quarterly profit as credit card spending collapsed.
Declining issues outnumbered advancers for a 1.70-to-1 ratio on the NYSE and for a 2.33-to-1 ratio on the Nasdaq.
The S&P index recorded eight new 52-week highs and no new low, while the Nasdaq recorded 19 new highs and 17 new lows.
By Medha Singh
