it seems incomplete to me.
You could say
By the year 2000, there had been 15 countries waiting to join the program, but the program was not yet ready to accept members...
there had been - implies that there is a change, or a length of time to their membership, and the length of time / end is important and relevant to what you are saying.
The first example is the best for a simple fact that is relates to a point in time.