US education system gives you an undergraduate degree in four years and thus is the requirements from international students to pursue any graduate school is completion of minimum of 16 years (10+2+4) of education.
Some business schools in the U.S. also accept a 3-year Indian Bachelor's Degree while others don't. If applicants hold a three year Bachelor's degree from an Indian university they would still be eligible to apply to schools like Wharton, Kellogg and Darden. Though you can be eligible to apply to these schools, these schools still mention that you would increase your competitiveness by obtaining a Master's degree before applying. It has to be your own decision, we have seen many successful applicants who have done well in their career, have a good extracurricular records and convey their case convincingly getting through these schools.
A post graduate diploma in the same area of study as your Bachelor's degree can qualify you for all MBA programs in the U.S. The completion of the 2-years Master's degree also completes the requirement. You would also be eligible if you are a member of the Institute of Chartered Accountants of India and hold a 3-year Bachelor's degree.
Schools that accept three year Indian undergraduate degree