Scarlett Johansson has admitted that working as a major character in the Marvel film universe is a huge undertaking.

The actress recently spoke about her upcoming film "Captain America: The Winter Soldier" and noted that the workload she had while filming was bigger than any other film she has done before.

"My first Marvel film was 'Iron Man 2' and then we did 'The Avengers' and then Chris Evans and I did ['Captain America: The Winter Soldier'], but I think that film, there's a couple of new characters," Johansson stated, according to Flickering Myth. "The Falcon [played by Anthony Mackie] is a new character in that, and of course Sebastian Stan is kind of continuing his character, obviously he's playing the Winter Soldier.

"But these characters really kind of take on something bigger than they've ever seen, so I think it's something that they can't do without each other," she added. "In that sense, we were in it, kind of neck-and-neck, and it's a bigger responsibility."

She also noted that the upcoming "Avengers: Age of Ultron" would bring a number of new challenges.

"But then again, even in Avengers 2, we all play in it, it's not like, 'Great, I'll be booking, like, two days a week and then be eating sandwiches the rest of the week,'" she noted about the workload for the sequel. "No, it's on. We all are fighting in it together, we're all fighting our own battles and our own demons and it's a lot of dramatic work, and the physical part of it, so the films all have their own challenges, but it's fun."

Johansson's character the Black Widow has appeared throughout the Marvel films since "Iron Man 2," but she has always been left in the background as a supporting character. She had a bigger role in "Avengers" but was overshadowed by the appearance of other major superheroes such as The Incredible Hulk, Iron Man, Captain America, and even Thor.

Now Johansson's Black Widow gets to be the leading lady in "Captain America: The Winter Soldier" and previous reports and comments from the lead actors have revealed that the character will develop an interesting relationship in the film.

"Their working relationship becomes a more intimate friendship," the actress said during the film's panel at Comic-Con back in July. "They have some unexpected similarities -- they both have their guard up, they have trust issues, and they've also both been working for 'the man' for their entire career ... Through this unexpected friendship that forms, they both start to question what they want."