NEW YORK (REUTERS) - United States (US) stocks slid for a second consecutive day on Tuesday after comments from a pair of US Federal Reserve officials left investors uncertain about the timing of a possible reduction in its bond-buying program.

Mr Dennis Lockhart, president of the Federal Reserve Bank of Atlanta, told Market News International in an interview that the Fed could begin trimming the size of the stimulus programme as soon as September, but might wait longer if the expected economic growth in the year's second half fails to materialise.

Later in the session, Chicago Fed President Charles Evans echoed the sentiment when he said the central bank will probably decrease the program later this year and could do so as early as next month, depending on the economic data.

Fed officials "are all hedging themselves, which is why the market continues to just be a little bit confused and why it is going to churn," said Mr Ken Polcari, director of the NYSE floor division at O'Neil Securities in New York.

"There is really no reason at the moment for the market to go higher because it is still too unclear."

One catalyst for Monday's downturn in the Dow and the S&P 500 was provided by Mr Richard Fisher, president of the Federal Reserve Bank of Dallas. He said he supported scaling back the central bank's stimulus next month unless economic data takes a turn for the worse.

The S&P 500's decline on Tuesday was its biggest fall since June 24 as investors continued to take profits from the recent rally that drove the Dow Jones industrial average and the benchmark S&P to back-to-back record closing highs late last week.

The Dow Jones industrial average fell 93.39 points or 0.60 per cent, to end at 15,518.74. The S&P 500 declined 9.77 points or 0.57 per cent, to 1,697.37. The Nasdaq Composite dropped 27.182 points or 0.74 per cent, to 3,665.77.

Earlier, the Dow fell as low as 15,473.40, while the S&P 500 touched a session low of 1,693.29, and the Nasdaq hit an intraday low of 3,654.672.

The S&P 500 has risen for five of the past six weeks, gaining more than 7 per cent over that period.

Volume was light for the second straight day, with about 5.5 billion shares traded on the New York Stock Exchange, NYSE MKT and Nasdaq, below the daily average of 6.36 billion. The thin volume exaggerated the market's swings.

Monday marked the lowest volume for a full-day session so far this year. With major US economic data like the nonfarm payrolls report and earnings from bellwethers out of the way, volume is expected to be light throughout the week.

The biggest drag on the Dow was International Business Machines Corp, down 2.3 per cent at US$190.99, after Credit Suisse cut its rating on the stock to "underperform" from "neutral."

The firm said growth would be a challenge for IBM in the future. Credit Suisse also cut its price target on the Dow component by US$25 (S$32) to US$175. IBM topped the list of the Dow's 10 worst-performing stocks.

Bank of America shares slid 1.1 per cent to close at US$14.64 after the US Justice Department and the Securities and Exchange Commission filed civil lawsuits against the bank for what government lawyers said was a fraud on investors involving US$850 million of residential mortgage-backed securities.

The stock was among the Dow's 10 bottom performers.

The S&P financial index tumbled 0.9 per cent.

Retailers' shares were among the day's biggest losers.

American Eagle Outfitters shares tumbled 12 per cent to US$17.57 a day after the retailer said its second-quarter profit would be hurt by weak sales and margins. A number of analysts downgraded the stock. The S&P retail index slipped 0.4 per cent.

Of the 418 companies in the S&P 500 that have reported earnings for the second quarter through Tuesday, Thomson Reuters data showed that 67.5 per cent have topped analysts'expectations, in line with the average beat over the past four quarters.

On the revenue side, the data showed that 54 per cent have reported revenue above estimates, more than in the past four quarters but below the historical average.

Declining stocks outnumbered advancing ones on the NYSE by a ratio of about 3 to 1, while on the Nasdaq, more than two stocks fell for every one that rose.