U.S. stocks retreated for a fourth day

U.S. stocks retreated for a fourth day, the longest since February, amid growing uncertainty about the U.K.'s future in the European Union and as investors awaited Wednesday's Federal Reserve announcement.

Equities fell, but not before staging a furious rebound amid gains in technology and consumer staples shares, rising from the day's lows in the final hour to pare much of the session's losses that reached as much as 0.7 percent in the S&P 500 Index.

The selloff is occurring just days after the S&P 500 hit its highest in almost 11 months, buoyed by optimism that low rates, steady job gains and modest growth would continue to support rising stock prices. Sentiment has shifted, with the potential fallout from a June 23 vote on Britain's membership of the EU increasingly unsettling global markets. Britain's largest-selling newspaper now backs a so-called Brexit, while five polls in the past 24 hours put the "Leave" campaign ahead of "Remain."

As policy makers and investors scrutinize data to weigh U.S. growth, a report today showed retail sales rose more than forecast in May, indicating consumer spending will help boost second-quarter growth. A separate gauge showed inflation pressures are building. The costs of goods imported into the U.S. climbed 1.4 percent in May, the biggest gain in four years.

Although traders are pricing in zero chance of a rate move tomorrow, Chair Janet Yellen's commentary afterward will be parsed for hints on the trajectory of borrowing costs. At least even odds for a rate increase have been pushed out to February 2017.

The S&P 500 had rallied as much as 16 percent from a 22-month low in February to within 0.6 percent of an all-time high, before its four-day slide amid growth worries and Brexit anxiety. The benchmark is less than 3 percent from its record set nearly 13 months ago, and has gone the longest without a fresh high outside of a bear market since 1984.

"Brexit is adding fuel to the fire for risk-averse investors," said Jasper Lawler, an analyst at CMC Markets Plc in London. "Markets are already worried about slowing global growth and the inability of central-bank policy to stem the decline. Global growth concerns are present because we don't know where the Fed is on that, but depending on the language they use, this could cause the market to gain again."