I plan to submit part of my current work to conference A. I then wish to submit my whole work to a more prestigious conference B. As for the part submitted to A, there is no point of repeating it again. So I will just cite my submission to A in my submission to B.

But the problem is that the submission deadlines for A and B are roughly the same. So actually the moment I submit the work to B, my partial work submitted to A has not been published yet. I have not even been notified of its acceptance.

Can I still cite it? My concern is that even if I can cite it, one will find nothing online.