US stock markets head lower following setback in Greek debt talks

U.S. stocks headed to losses on Friday as a setback in talks between Greece and its creditors heightened concerns that the country could default on its debts. An unexpected decision by the International Monetary Fund to walk away from talks with Greece spurred the selloff in Europe.

KEEPING SCORE: The Dow Jones industrial average fell 75 points, or 0.4 percent, to 17,964 as of 10:05 a.m. Eastern Time. The Standard & Poor's 500 slipped eight points, or 0.4 percent, to 2,101, and the Nasdaq composite lost 15 points, or 0.3 percent, to 5,067.

PEEP THIS: Twitter announced late Thursday that CEO Dick Costolo will step down. The move follows growing criticism of the company's financial performance. Co-founder Jack Dorsey, who served as CEO during Twitter's early years, will temporarily take the reins while the San Francisco messaging service looks for a permanent replacement. Twitter jumped 67 cents, or 2 percent, to $36.51 early Friday.

WALKOUT: At a summit meeting in Brussels on Thursday, the IMF pulled its negotiators out of talks with Greece, saying there had been no progress and that major differences remained on key issues. Without a deal by the end of the month, Greece faces the prospect of going bankrupt and dropping the euro currency.

EUROPE: Major indexes in Europe slumped, erasing gains made earlier in the week. Greece's market fell the most, with the main Athens index down 3 percent. Germany's DAX fell 1.8 percent, and the CAC-40 in France dropped 2 percent. Britain's FTSE 100 sank 0.7 percent.

ONE TAKE: "One side is going to have to offer some serious concessions if a deal is going to be reached," said Craig Erlam, senior market analyst at OANDA.

ASIA'S DAY: Japan's Nikkei 225 inched up 0.1 percent. In China, the Shanghai composite index advanced 0.9 percent, and Hong Kong's Hang Seng rose 1.4 percent.

CRUDE: Benchmark U.S. crude sank 77 cents to $60.01 a barrel in New York. Brent crude, a benchmark for international oil, fell 31 cents to $65.48.

BONDS: U.S. government bond prices edged up, tugging down the yield on the 10-year Treasury note to 2.37 percent from 2.38 percent the day before. Bond yields fall when prices rise.