Source: Jimmy Fallon Closes NBC 'Tonight Show' Deal, Seth Meyers Eyed for 'Late Night'

When exactly Fallon will replace Jay Leno on "Tonight" remains unclear as NBC debates when to announce the transition.

Jimmy Fallon's march to inherit The Tonight Show is nearly complete. The Late Night host has closed a new deal with NBC that will pave the way for him to replace Jay Leno in the 11:35 p.m. slot, a well-placed source tells The Hollywood Reporter.

Fallon’s move has been expected since THR revealed March 1 that NBC was preparing an exit plan for Leno, 62, whose contract expires in September 2014. But NBC has refused to confirm the succession, instead letting Leno and Fallon, 38, tease audiences with jokes about the situation.

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The duo sang an amusing on-air duet April?1, mocking NBC’s late-night uncertainty and suggesting both hosts are comfortable with the transition -- or at least more comfortable than NBC's 2009 shift from Leno to Conan O'Brien. NBC and Fallon’s CAA reps declined comment.

Still not clear is when exactly Fallon will take over Tonight. THR’s source says some NBC execs want to launch Fallon’s New York-based Tonight in February during network's high-rated Winter Olympics coverage, but producer Lorne Michaels is said to prefer to give Fallon a little more time. Plus, NBC would owe Leno a significant penalty if it took him off the air before his contract expires.

The timing and nature of the Fallon announcement also is said to be in flux, with some at NBC said to believe that the network should wait to confirm the Tonight transition until it can close a deal with Fallon’s replacement.

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The strong frontrunner for that 12:35 a.m. job is said to be Saturday Night Live stalwart Seth Meyers, who could be installed as the new Late Night host when Fallon takes over Tonight. Meyers, like Fallon and his predecessor, Conan O’Brien, is a Michaels protege. "It will be Seth unless something goes awry [in the dealmaking,]" says a source close to the situation.

Until the shift is made official, Leno and Fallon are expected to continue their mockery of the transition. Tonight has been up in the ratings since Leno began his recent NBC ribbing.

Email: Kim.Masters@thr.com

Twitter: @KimMasters