YEREVAN, August 27. /ARKA/. U.S. stocks fell, with the Standard & Poor’s 500 Index’s halting two days of gains, after Secretary of State John Kerry said the president will hold Syria’s government accountable for using chemical weapons.

Tyson Foods Inc. (TSN), the largest U.S. meat processor, slid 7.3 percent after Bank of America Corp. analysts cut their rating on the stock. Archer-Daniels-Midland Co., the largest corn processor, dropped 4.9 percent as hot, dry weather in the Midwest threatened to reduce crop harvests. Amgen Inc. jumped 7.7 percent after agreeing to buy cancer-treatment developer Onyx Pharmaceuticals Inc. in a $10.4 billion transaction.

The S&P 500 declined 0.4 percent to 1,656.78 at 4 p.m. in New York, erasing an earlier gain of as much as 0.4 percent. The Dow Jones Industrial Average lost 64.05 points, or 0.4 percent, to 15,946.46.

“If there’s going to be turmoil and then if there’s going to be some retaliation and affect U.S. assets, people get a little scared,” Frank Ingarra, head trader at Greenwich, Connecticut-based NorthCoast Asset Management LLC, said in a phone interview. “It’s a bit of a pullback so people are probably taking some risk off the table.”

President Barack Obama is consulting with allies and members of Congress and “believes there must be accountability for those who have used the world’s most dangerous weapons,” Kerry said. –0--