MENLO PARK, Calif. — Facebook’s long-rumored plan to directly host articles from news organizations will start on Wednesday, concluding months of delicate negotiations between the Internet giant and publishers that covet its huge audience but fear its growing power.

Nine media companies, including NBC News and The New York Times, have agreed to the deal, despite concerns that their participation could eventually undermine their own businesses.

The program will begin with a few articles but is expected to expand quickly. Users of iPhones will see glossy cover videos and photos tagged with map coordinates. Most important for impatient smartphone users, the company says, the so-called instant articles will load up to 10 times faster than they normally would since readers stay on Facebook rather than follow a link to another site.

Facebook has gone to unusual lengths to court the publishers participating in the project, some details of which were previously published by The New York Times and The Wall Street Journal.