🚀 go-pugleaf

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I hope that I have the correct newsgroup. I'm looking for a solution to the
following puzzle, or proof that it cannot be solved:

A and B are two people at two ends of a very slow telephone connection. 
They are both completely cut off from the world except for their connection 
with each other.  In particular, they have no idea what time it is in the 
real world.

There is a delay AB in the transmission of what is being said by
A to B, and a delay BA in the transmission of what is being said
by B to A. The delay AB does not equal the delay BA. The delays, for the
purpose of this problem, are on the order of minutes in each direction.

Both A and B have watches. Before they begin to talk, the watches are not
set to the correct time, nor are they set to the same time.

The problem is to devise a procedure such that A and B can, via their 
telephone connection only, accurately synchronize their watches (to
within a few seconds). The watches do not have to reflect time in the
real world, but must match each other. Both A and B will know the procedure 
before the call begins, and each will know whether he is A or B.

Thanks for any help.