The artwork sees the pair looking wary, with Stark's Iron Man armour damaged and Pepper putting a hand on his chest as he circles a protective arm around her.
Meanwhile Downey Jr. has revealed that he and director Shane Black called on JJ Abrams for help with the movie's script at several times during the writing process.
He told IGN: "There were a couple times in Iron Man 3 where our lifeline was we'd call Jon Favreau.
"Then we reached out to JJ Abrams at one point when we were really confused in Act III, and he helped us, too."
The film's UK release date has been moved a day earlier, to 25 April.
A new trailer was released yesterday.
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