Can US scientists travel to Cuba?

[PRAKASH at ACD.TUSK.EDU]

As the header says, I want to know from any of you
what is the current position of US Govt. on travel to 
Cuba.  I recognize that there is a ban on travel to
Cuba since Kennedy Administration times (infact, I believe
one could be in great legal trouble by going to Cuba).
Is there any change in the policy now?

A biotech conference is being held in Havana this November
and I have been invited to attend.  There a couple of
groups in Cuba working on sweetpotato biotechnology
and I am intersted in knowing more about their work first hand.
All my grants are from US agencies such as USDA.

Can some one please throw more light on this issue?

Thanks!

-C. S. Prakash
Tuskegee University