A fourth hour of the “Today” show is an official “go.” NBC is expected to announce this week.

The fourth hour – which The Post reported last month was a “virtual certainty,” will launch in September and will air in New York at 10 a.m.

NBC isn’t ready to announce what will be dropped to make way for the new fourth hour, nor who the new hosts will be.

But you can count Lara Spencer out of the mix.

“The Insider” co-host has inked a new, multi-year deal to remain on the syndicated entertainment show, owned by CBS.

Matt Lauer and Meredith Vieira host the first two hours of “Today,” with Al Roker and Ann Curry taking over from 9 to 10 a.m.

“The Martha Stewart Show” currently airs at 10 a.m. in New York. – Michael Starr