-By John Consoli, Mediaweek

NEW YORK NBC Sports sales today said NBCU TV networks are 90 percent sold out of their Summer Olympics inventory, having sold $900 million worth of ad time. Reaching $1 billion would break previous sales records for Olympics telecasts.

There were rumblings earlier this year that NBC's ad sales for the Beijing Olympics, which begin in mid-August, were lagging behind previous years. But the latest announcement says that is no longer the case.

"Advertisers across all categories are recognizing the power of premium content and the strength of the Olympic brand," said Seth Winter, svp, NBC Sports & Olympics. "Live sports continues to resonate with viewers, and advertisers know the Olympics are one of the best ways to reach an engaged mass audience."

Hot categories that have seen the most spending in the past few weeks, according to Winter, are consumer electronics, corporate image campaigns, movies and retail, the latter category spurred by back-to-school ads.

Winter said NBC's recent airing in prime time of the U.S. Olympics trials for swimming, gymnastics and track and field, have created more viewer buzz and motivated more advertisers to jump on board for the regular Games coverage next month.

NBC will televise 3,600 hours of Olympics coverage on the NBC broadcast network, NBCU's various cable networks and NBC.com. NBCU will cover every Olympic sport for the first time ever.