Rejoice, Tony Stark fans: Robert Downey Jr. is nearing a deal to star in "Captain America 3."

The "Iron Man" star is in final negotiations to reprise his role as the metallic superhero in the forthcoming Marvel threequel, in a storyline that will pit him against Chris Evans' star-spangled superhero, according to Variety.

Lifted from the "Civil War" crossover plot that spanned a seven-issue limited series in 2006-7 (and will be rebooted next year), the film will see Stark and Rogers grappling over their differences concerning the Superhero Registration Act, a program that requires anyone with superhuman abilities to register and serve as crimefighters for the U.S. government. In the comics Rogers is against the program while Stark advocates for it, casting the latter in somewhat of an antagonistic role. The storyline will be introduced in "Captain America 3," which is slated to begin production in the spring for release on May 6, 2016.

Downey, who Variety reports will receive in the ballpark of $40 million plus backend participation for starring in the threequel, is also slated to appear in "Avengers: Age of Ultron" and its followup "Avengers 3" ("Iron Man 4" remains a question mark).

Tony Stark was allegedly supposed to play only a small part in the Joe and Anthony Russo-directed "Cap 3" until Downey stated his desire to take on a meatier role in the plotline, a stance initially balked at by Marvel Entertainment CEO Ike Perlmutter (according to the Variety article). He was ultimately swayed by Marvel Studios president Kevin Feige, however, leading to the impending deal.

The "Civil War" plotline is being viewed as a driver for the Marvel franchise's interlocking stories over the next seven years. Phase Three kicks off with next summer's "Ant-Man," which hits theaters on July 17, 2015. "Avengers: Age of Ultron," meanwhile, is slated for release on May 1.

Are you glad Robert Downey Jr. is playing a major role in "Captain America 3"? Let us know in the comments.

A former contributor to sites including MTV's The Backlot and Bloody-Disgusting, Chris Eggertsen worked in film development before indulging his love of pop culture writing full time. He specializes in horror, the intersection of social issues and entertainment and Howard Stern. He's on Twitter @HitFixChris.