Gibbs said that Mr. Obama has been "struck" by the images coming out of the protests in Iran.
"I think we can hear their voices all the way over here and well beyond. I think the president has been struck by many of the images he's seen, particularly those images of women speaking out for their rights," Gibbs told co-anchor Harry Smith. "I think we've all been struck by that, and I think the president has talked about ensuring justice in Iran."
Gibbs added: "He made it very clear in our conversation last Friday the whole world's watching."
CBS News White House correspondent Peter Maer reports that Gibbs earlier told CBS News that Mr. Obama's opening statement this afternoon will include "stern words" about the violence in Iran. Mr. Obama will also open with comments on his health care reform and energy initiatives.
Also of note: The White House just now moved the press conference from the Rose Garden to the briefing room. Aides tell CBS News White House correspondent Mark Knoller the event was moved inside because it will be too hot in the Rose Garden. Forecasts put the high at around 82 degrees today in the nation's capital, under party cloudy skies.
You can watch the The Early Show video with Gibbs below, where he also addresses whether the president has quit smoking:
For all the latest breaking news on Iran from CBS News, click here for our Iran Watch.
Mr. Obama's press conference will be live on this site at 12:30 p.m. ET. And stay tuned on CBSNews.com following the event for a special edition of "Washington Unplugged" with instant analysis of the president's comments.