US stocks dropped early Friday on renewed worries over a potential Greek debt default as Twitter shares gained on news chief executive Dick Costolo would step down.
About 35 minutes into trade, the Dow Jones Industrial Average was at 17,958.53, down 80.84 points (0.45 percent).
The broad-based S&P 500 fell 8.39 (0.40 percent) to 2,100.47, while the tech-rich Nasdaq Composite Index lost 16.34 (0.32 percent) at 5,066.17.
Equity markets in Britain, France and Germany fell sharply after the International Monetary Fund withdrew from talks with Greece, saying a deal was far off.
Twitter gained 1.2 percent after announcing that co-founder Jack Dorsey would step in on an interim basis to lead the microblogging company. Analysts had criticized Costolo for disappointing growth at Twitter.
Google fell 0.5 percent as a French regulator ordered it to take action to extend Europe's "right to be forgotten" worldwide, escalating a fight with the technology giant.
T-Mobile US rose 1.6 percent on reports that Dish Network is in talks with banks to provide as much as $15 billion in financing for a takeover bid. Dish dropped 1.1 percent.
Eli Lilly shares fell 2.6 percent on a mixed reaction to clinical data released on Baricitinib, a treatment for rheumatoid arthritis. Credit Suisse said the results were "encouraging" but that more data was needed to assess the long-term safety profile of the drug.
Bond prices were mixed. The yield on the 10-year US Treasury rose to 2.39 percent from 2.38 percent Thursday, while the 30-year held steady at 3.10 percent. Bond prices and yields move inversely.