The Iron Man 2 casting train just keeps on chugging along. According to Variety, Emily Blunt has emerged as a leading candidate to portray the femme fetale Black Widow in Iron Man 2.

Blunt would portray Natasha Romanoff, a Russian spy by day and Black Widow, a sultry villain in a skin-tight black suit with high-tech gadgetry, by night. Marvel Studios wouldn't comment on Black Widow's casting at this time.

It was recently announced that Mickey Rourke and Sam Rockwell were in negotiations to portray other villains in Jon Favreau's highly-anticipated sequel to this summer's blockbuster Iron Man.

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Production is said to get under way this spring and they're aiming at a May 7, 2010 release for the sequel.