It's EB2-NIW, which I have. You must have articles with a large number of citations. You can be a second author, but you must demonstrate that your work was significant and equal to that of the first author. I believe you will also require a strong recommendation(i think most important) demonstrating that your work has been used by them. It makes no difference where you come from.

@aksshre : Thank you so much for your input. The only dilemma I have is the weight they carry. Eg. X has papers with lots of citations but lesser job experience. Y has paper with few citations, however, worked for an important US government organization (DOH etc). Which one do you think will get preference? Thanks again!

It makes little difference since you should explain at least three research projects you have completed/published and obtain a recommendation letter for each. If your work was used in the DOJ, obtain a letter of recommendation from them detailing how they used your work. In my situation, I received five recommendation letters: two from dependents who worked with me, and three from independents who used my work but did not collaborate with me. Obtain a letter of recommendation on their official letterhead if possible. I had 10 publications at the time of application, including journal and conference articles, and had accumulated around 80 citations. I would advise you to publish more of your work as a first author so that you can build up some citations.

@aksshre : Great! Really appreciate what you've shared. Sure, will work towards publishing more! Thanks!