NBC Sports' Olympic ad sales for Rio are 20 percent more than for the London Summer Games, at $1.2 billion with the games about to open officially Friday, a top executive said on Thursday.

Seth Winter, executive vice president of advertising sales for Comcast Corp.-owned NBC Sports, said that the media company was "pretty much sold out of premium inventory" - which means prime-time spots on the NBC broadcast network - and that he was "exceptionally bullish on the games."

Ironically, Winter said, issues related to the games in Brazil - such as polluted water for swimmers and the Zika virus - have heightened the public's awareness of the Olympics and could lead to the bigger audience that advertisers are looking for with commercials.

"The stories on the issues have really helped us, we believe," he said.

Digital advertising sales are up about 33 percent compared with the London Olympics, and Winter noted that several advertising categories will have strong representation in ad sales during the games, including autos, telecommunications, movies, insurance, and drugs.

Winter also said there would be political ads aired during the Olympics, but he declined to say which candidates had spots.

As in previous Olympics, about 75 percent of the advertising dollars will be earned during prime time on NBC, which is watched by millions of households and is expected to dominate the ratings during the games, which will end Aug. 21. Because Rio de Janeiro is only one hour ahead of the East Coast, these will be the most-live Olympics televised during prime time since the 1996 summer games in Atlanta, NBC officials say.

In addition to its broadcast and cable TV networks and websites, NBCUniversal has struck deals to post highlights and other content on Google, Facebook, Instagram, and Snapchat. The goal is to reach a younger audience with those platforms.

Winter said advertising revenue related to those platforms was not included in the $1.2 billion ad-sales figure.

NBC plans to televise or stream about 7,000 hours of coverage across multiple networks and platforms. There will be about 2,000 employees in Rio and an additional 1,000 at NBC Sports headquarters in Stamford, Conn.