Review paper authored by a current collaborator I have a simple question about a math paper, since I don't have a lot of experience in reviewing papers. I have currently received a request for reviewing a paper for publication. I would normally have no problem in doing so.

The thing is that I am currently about to start a collaboration with one of the authors of this paper. This collaboration even appears mentioned at some point in the paper that I was asked to review (in the lines of "the author ... and ... are planning to ...", where one of the ... is me).

I wonder whether there is an ethical dilemma. Perhaps it's completely normal and standard and I'm just making a big deal out of it. I'm sure it depends on the discipline, so I wanted to hear about this from people in the math world. Thanks!
If one author is too close to you, you should decline. I do not review for recent co-authors and current collaborators of mine but I start collaborations with people I reviewed.