Full Idea
I suggest that every grammatically significant indicative sentence expresses a 'statement', but the word 'proposition' will be reserved for what is expressed by sentences that are literally meaningful.
Gist of Idea
Sentences only express propositions if they are meaningful; otherwise they are 'statements'
Source
A.J. Ayer (Introduction to 'Language Truth and Logic' [1946], p.10)
Book Reference
Ayer,A.J.: 'Language, Truth and Logic' [Penguin 1974], p.10
A Reaction
We don't have to accept Ayer's over-fussy requirements for what is meaningful to accept that this is a good distinction. Every day we hear statements from people (e.g. politicians) in which we can fish in vain for the underlying proposition.