Most PhD programs don't care if you have done an MBA and some might see it as a negative signal since it is so industry-oriented. (A masters in econ, finance, stats, OR, or something else is seen as a much stronger signal.)
Also, some PhD programs offer an MBA as an easy option on the way to a PhD. Some make you do it on the way if they want to be able to kick you out before graduating without them feeling guilty. (I know of one program where them asking you to do the MBA on the way is a sign you are in trouble.)
rango
Hi siddhartha;
Its very commendable that you want to go for PHD in top B school in USA. But i make you one thing clear, the B school PhD programme is full time and very rigorous. No external jobs are allowed. You may get a teaching assistant ship at the university level.
Thanks

Very true. There is no way you can work an outside job and do a PhD; and, even if you could, the political damage of not being around most of the time would be fatal. To pass quals, you need to do well AND at least one faculty member has to want to do research with you. If you are rarely around, none of them will know you well enough to gamble on doing research with you.
Best of luck; I hope things work out well!