I have received a review request from a journal (in case it matters, it is the best journal in a certain field of mathematics). The article has some material in which I can reasonably be considered an expert (because I myself have published something related in the same journal) whereas some other aspect of the article is beyond my comfort zone.
Therefore, I am thinking of responding to the request affirmatively under the provision that there is some other reviewer who can better review the latter aspect of the paper. My question for this site is whether or not if this is a common and/or acceptable reply to a review request.
A related issue is that the Web editorial system is set up so that a comment to the editor is solicited only if a review request is declined. I'm not sure if I want to decline the request solely to talk to the editor and cost the authors a few more weeks of administrative time.