U.S. stocks declined, with the Standard & Poor’s 500 Index on the verge of its worst month in more than three years, as investors harbored concerns about slowing global growth and the impact of a potential interest-rate increase by the Federal Reserve as soon as September.

Equities earlier trimmed their losses after energy shares reversed a 2.5 percent selloff to rally as much as 1.4 percent. The move followed a jump in oil prices after a government report reduced its crude production estimates. Equities trading has been whipsawed by gains and losses since last week as markets remain subject to sudden shifts in investor sentiment.

The S&P 500 lost 0.5 percent to 1,979.98 at 12:13 p.m. in New York, after earlier falling as much as 1.2 percent before trimming the drop to less than 0.2 percent. The Dow Jones Industrial Average sank 55.42 points, or 0.3 percent, to 16,587.59. The Nasdaq Composite Index slipped 0.4 percent.

The S&P 500 is down 5.9 percent this month, remaining on pace for the most since May 2012, as China’s currency devaluation earlier this month spurred concern over global growth, erasing more than $5.3 trillion in equity market values worldwide. The benchmark’s 0.9 percent gain last week masked a volatile period in which the S&P 500 plunged the most since 2011 to enter a correction, only to rally more than 6 percent over two days for its best back-to-back gains since the beginning of the bull market in 2009.

The Chicago Board Options Exchange Volatility Index rose 7.3 percent Monday to 27.96. The measure of market turbulence known as the VIX is on its way to a record monthly jump, up 127 percent. More than $2 trillion of share value was erased from U.S. markets between the end of July and the lowest levels of last week, a sum equal to roughly two years of S&P 500 earnings, data compiled by Bloomberg show.

While August ranks in the middle among months based on share performance, it has produced some of the worst returns of the year since 2009. During the week ended August 12, 2011, the S&P 500 alternated between gains and losses of at least 4 percent for four days, something never seen in 88 years of data compiled by Bloomberg. In 2013, the S&P 500 fell 3.1 percent in August, one of only two months of negative returns in a year when the index surged 30 percent.

Source : Bloomberg