US stocks end week on a down note

US stocks closed a choppy week on a down note Friday, following European markets lower on fears of a Greek debt default.

At the closing bell, the Dow Jones Industrial Average was at 17,901.04, down 138.33 points (0.77 percent).

The broad-based S&P 500 fell 14.73 (0.70 percent) at 2,094.13, while the tech-rich Nasdaq Composite Index dropped 31.41 (0.62 percent) to 5,051.10.

European equity markets tumbled as eurozone officials confirmed that at a meeting in Bratislava on Thursday they had war-gamed "worst case" scenarios of Greece not being able to pay its bills.

Peter Cardillo, chief market economist at Rockwell Global Capital, said the latest headlines on the breakdown in talks between Greece and creditors are "very negative," while adding: "It goes back and forth and is basically an excuse for the market."

Cardillo said there are other factors behind the pullback in US equities, including next week's Federal Reserve policy meeting that will update the Fed's plan to hike interest rates in the coming months.