U.S. stock indexes opened more than 1 percent higher on Monday as investors welcomed AT&T's proposal to buy T-Mobile USA from Deutsche Telekom, a deal that would create the largest mobile operator in the United States.

Glimmers of hope about Japan's nuclear crisis and investor Warren Buffett's comments about a buying opportunity for Japanese stocks also boosted investor sentiment.

The Dow Jones industrial average <.DJI> was up 163.02 points, or 1.37 percent, at 12,021.54. The Standard & Poor's 500 Index <.SPX> was up 16.44 points, or 1.29 percent, at 1,295.64. The Nasdaq Composite Index <.IXIC> was up 36.02 points, or 1.36 percent, at 2,679.69.

(Reporting by Caroline Valetkevitch; Editing by Padraic Cassidy)