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.

RELATED: Marvel Movies Are 'Crap' According to Iron Man 2 Star Mickey Rourke

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.

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