Set transaction isolation level read uncommitted?

I have a particular situation where I _want_ a transaction to see the effect of uncommitted writes (please don't tell me that I shouldn't be doing this -- it's in a very controlled environment). Is it possible in Informix to set the transaction isolation level of a read-only transaction to read uncommitted, so that the transaction sees the uncommitted writes of other ongoing transactions? (In Oracle I have found that it is not possible.) -Dallan