NEW YORK ( TheStreet) -- U.S. stocks fell Friday extending June's decline to 1.5%, the first monthly retreat for the S&P 500 since October as investors struggled to sort through the mixed messages from Federal Reserve officials about a timeline for curbing the central bank's stimulus measure.

The S&P 500 fell 0.4% to close the month at 1,606.28. The index rose 0.87% for the week. The Dow Jones Industrial Average dropped 0.8% to 14,909.66. The blue-chip index increased 0.74% for the week. The Nasdaq gained 0.04% to 3,403.25. The tech-heavy index jumped 1.4% over the past five trading sessions.

Confusion about the Fed's schedule for winding down its quantitative easing program increased Friday after Federal Reserve Governor Jeremy Stein indicated the central bank could begin curbing its bond-buying program in September, which somewhat went against the comments from other Fed officials this week that tapering would be very gradual.

Elsewhere, Richmond Fed President Jeffrey Lacker said during an economic outlook speech in White Sulphur Springs, West Virginia to expect volatility to stay in the markets so long as the debate on the timeline for reducing the asset purchases was ongoing. Following up on Stein's views, Lacker said he was skeptical of the notion that there could be any additional benefits from the continuation of the bond buying and was more concerned about the potential risks tied to further balance sheet expansion.

The benchmark 10-year Treasury was falling 6/32, boosting the yield to 2.493%.

During a speech on monetary policy to the Council on Foreign Relations in New York, Stein urged investors to not look so much nonfarm payrolls data that is released going into the month's meeting. He cautioned that any move by the central bank to wind down stimulus will likely be decided according to economic numbers that preceded those jobs numbers and had been released since the Fall 2012 period when QE3 was launched, in assessing the overall U.S. recovery and in order to lessen potential volatility in the markets.

"The best approach is for the Federal Reserve to be clear that in making a decision in, say, September, it will give primary weight to the large stock of news that has accumulated since the inception of the program and will not be unduly influenced by whatever data releases arrive in the few weeks before the meeting ... as salient as these releases may appear to be to market participants," Stein commented.

"Even if a data release from early September does not exert a strong influence on the decision to make an adjustment at the September meeting, that release will remain relevant for future decisions," he said. "If the news is bad, and it is confirmed by further bad news in October and November, this would suggest that the 7% unemployment goal is likely to be further away, and the remainder of the program would be extended accordingly."

Accenture ( ACN) plunged 10.3% to $71.96 after the company gave a disappointing outlook on both sales and earnings, forecasting current quarter revenue of $6.7 billion to $7 billion, which was below the average analyst estimate of $7.4 billion. Full-year earnings outlook was cut to $4.18 to $4.22 a share and missed the consensus estimate of $4.30 a share. For its fiscal third quarter, revenues barely budged and were worse than expected as its consulting results turned out lackluster amid weakness in its European market and communications, media and technology unit.

BlackBerry ( BBRY) shares plunged 27.8% to $10.46 after the company missed Wall Street's top- and bottom-line estimates in its first-quarter results on Friday. The smartphone maker reported revenue of $3.1 billion, up from $2.8 billion in the prior year's quarter, but below analysts' forecasts of $3.36 billion. BlackBerry reported a loss from continuing operations of $84 million, or 16 cents a share, compared with a loss of $510 million, or 97 cents a share, in the prior year's quarter.

Computer Sciences Corp. ( CSC) fell 2% to $43.77 after the Navy said Thursday that Hewlett-Packard ( HPQ) beat a number of contractors including Computer Sciences in winning a $3.5 billion contract to operate the Navy's communications network through 2018.

Biogen Idec ( BIIB ) added 3.1% to $215.20 as it continued to win favorable opinions on Wall Street. Earlier in the week, Jefferies analyst Corey Davis wrote in a client note that the company's multiple sclerosis treatment Tecfidera was threatening the market share of competitors such as Teva Pharmaceutical's ( TEVA ) Copaxone.

Economic numbers Friday were mixed with bright spots.

The headline number on the Chicago Purchasing Managers Index release on Friday pointed to a deterioration in business conditions in the Chicago area. The gauge declined to a worse than expected 51.6 in June from 58.7 in May. On average, a drop to 56 was expected, according to a Thomson Reuters poll of economists. However, the employment index component of the report showed a rise to 57.8 from 56.9.

The final estimate on the University of Michigan Consumer Sentiment Index came in better than expected at 84.1 in June vs. the prior estimate of 82.7. Economists had predicted no changes in the final estimate.

Written by Andrea Tse and Joe Deaux in New York

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