U.S. stocks erased gains in a late-day collapse after the Federal Reserve held pat on interest rates, with mixed American growth and a sluggish global economy heightening concern the effectiveness of central-bank stimulus has reached its limits.

The S&P 500 Index fell 0.2 percent to 2,071.82 at 4 p.m. in New York, erasing a climb of 0.5 percent, and posting a fifth straight drop, the longest since February. Losses accelerated in the final half hour of trading after crude oil sold off.

"The Fed scaling back the indicated pace of rate hikes can be construed as them not seeing requisite strength -- there's a malaise that's set into the economy," said Bill Schultz, who oversees $1.2 billion as chief investment officer at McQueen, Ball & Associates Inc. in Bethlehem, Pennsylvania. "Without something to push equities higher, besides low rates, we're losing steam here. With uncertainty around the British vote later this month, the path of least resistance seems to be down at this point."