Wall Street posted its third straight week of gains on Friday, lifted by optimism ahead of this weekend's summit of European leaders and strong earnings from blue-chip stocks.

Based on the latest available data, the Dow Jones industrial average <.DJI> was up 267.62 points, or 2.32 percent, at 11,809.40. The Standard & Poor's 500 Index <.SPX> was up 22.98 points, or 1.89 percent, at 1,238.37. The Nasdaq Composite Index <.IXIC> was up 38.84 points, or 1.49 percent, at 2,637.46.

For the week, the Dow was up 1.3 percent, the S&P 500 was up 1.1 percent and the Nasdaq was down 1.1 percent.

(Reporting by Caroline Valetkevitch; Editing by Kenneth Barry)