Robert Downey Jr is in final negotiations to reprise his role of Iron Man in the upcoming third installment of Marvel’s Captain America franchise.

The 49-year-old actor would play a major role in the film’s Civil War storyline in which Iron Man and his alter-ego Tony Stark face-off against Captain America and his alter-ego Steve Rogers played by Chris Evans, according to a report on Monday by Variety.

The Civil War storyline follows superheroes as they take sides following the implementation of the government’s Superhero Registration Act that forces anyone with superhuman powers to reveal their identities and agree to act as a police force for the government.

New adventure: Robert Downey Jr reportedly was in final negotiations to reprise his role as Iron Man in Captain America 3

World War II hero Rogers opposes the program due to its threats to civil liberties while industrialist Stark supports it.

Marvel released a teaser Civil War poster on Monday showing Iron Man and Captain America both pulling on Spider-Man.

Spider-Man in the Civil War comic book series in 2006 initially supported the Superhero Registration Act and dramatically took off his mask to reveal his identity as Peter Parker.

Taking sides: Chris Evans, shown in Captain America: The Winter Soldier, faces off against Iron Man in the Civil War storyline

The teaser poster had a Summer 2015 tagline indicating that Marvel was planning on reviving the storyline.

Captain America 3 has been scheduled to begin production next spring with a release targeted on May 6, 2016.

Downey will appear as Stark/Iron Man in The Avengers: Age Of Ultron due out in May 2015 and has agreed to star in The Avengers 3.

Caught in the middle: Iron Man and Captain America pull on Spider-Man in a teaser for the Civil War storyline released on Monday by Marvel

The actor last week told chat show host Ellen DeGeneres that he would be starring in an Iron Man 4, but later backtracked during an appearance on The Late Show With David Letterman.

Variety reported that Marvel wanted Downey for a smaller role in Captain America 3, but the actor wanted a more substantial part.

Sources said Marvel Entertainment chief Ike Perlmutter was angered by that and ordered screenwriters to write Iron Man entirely out of the script before both sides reached an agreement.

Downey would earn about $40 million plus backend incentives for Captain America 3, sources said.