NEW YORK (TheStreet) -- Stocks extended modest losses by the final hour of trading on Friday as continuing Greek debt talks worried investors.

The S&P 500 was down 0.46%, and the Dow Jones Industrial Average fell 0.52%. The Nasdaq slipped from its record close on Thursday, down 0.31%.

Crude oil closed with daily and weekly losses as the safe-haven U.S. dollar moved higher against international currencies. West Texas Intermediate crude dropped 1.4% to $59.61 a barrel, down 0.6% for the week. Exxon Mobil (XOM), Schlumberger (SLB), Chevron (CVS), Halliburton (HAL) and ConocoPhillips (COP) fell, while the Energy Select Sector SPDR ETF (XLE) slid 0.92%.

The European Central Bank reportedly raised its funding cap on Emergency Liquidity Assistance for Greece's banks, according to Reuters. Greek savers reportedly pulled 1 billion euros out of banks in a single day on Friday.

"There is a sense of unease in the markets as the clock continues to tick down to the approaching deadline for Greece to strike a deal to avoid a debt default," said TD Securities' Millan Mulraine.

European Council President Donald Tusk has called an emergency summit for further debt talks on Monday. Eurozone finance ministers from 19 countries will convene to try to overcome the stalemate. Eurozone finance ministers want Greece to introduce a round of austerity measures in exchange for further debt relief. Greece has until the end of the month to repay its debts to the International Monetary Fund. Click here for more.

ConAgra Foods (CAG) led the S&P 500, adding 9.8% on news Jana Partners had taken a 7.2% in the company. The activist investor argued the company's shares are undervalued and is seeking a change in its board.

San Francisco Federal Reserve President John Williams said the economy appeared strong enough to support a rate hike in a speech on Friday. However, he remains in wait-and-see mode until inflation data improves.

"I still believe this will be the year for liftoff, and I still believe that waiting too long to raise rates poses its own risks," he told an audience in San Francisco.

Hershey (HSY) slid 3.5% after the chocolate company reduced its 2015 forecast on weakened growth in China. The company expects full-year earnings of $4.10 to $4.18 a share, below estimates of $4.31 a share.

KB Home (KBH) added nearly 11% after second-quarter profit and sales beat estimates. The homebuilder earned 10 cents a share, 2 cents higher than expected, while revenue of $622.97 million jumped 10.3% from a year earlier.

Fitbit (FIT) shares extended Thursday's gains, climbing 10.2%. The wearable tech company surged in its market debut on the New York Stock Exchange on Thursday, rocketing 48% higher to $29.68, well above its initial pricing of $20 a share for its float of 36.6 million shares.

Sequential Brands (SQBG) and Martha Stewart Living Omnimedia (MSO) were on watch after a late-day surge a day earlier. The two gained on a Wall Street Journal report that Sequential Brands was nearing an agreement to purchase Martha Stewart for an undisclosed amount. 

CarMax (KMX) slid nearly 3% after reporting in-line quarterly earnings and a revenue miss. The car dealership reported a 4.9% increase in used unit sales at comparable stores.

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