Reviewer wants me to do x - Should I admit I don't have the resources to do so although I think it's a good idea? A reviewer pointed out that I should do an additional experiment to further validate my analysis. I agree this would be a good idea and would further strengthen the manuscript. However, I think it belongs to the category "a paper can always be better" and I don't think the additional experiment is essential to my argument.

The main reason I am not doing the additional experiment is that it would require additional funding that I don't have, and cannot acquire in the time the journal wants me to submit a revised version of the article (and even if they were more flexible, it would not be a good idea to wait two years to submit a revised version).

What is my best strategy when replying to the reviewer's comments? Should I


point out that adding the additional experiment would require additional funding and that this would not be possible within a reasonable time frame?
point out that the results are meaningful even without it?


I am a bit worried that saying "yes, that's a good idea, but I don't have the means to do it right now" would trigger the reply "Well, that's too bad for you, then the article is not suitable for publication". What's the best strategy here?
When I have been faced with a situation like this in the past, the course of action that my co-authors and I found best was to get in touch with the handling editor to negotiate.

Editors are the ones who will generally make the call, and if doing the experiments will pose an high burden in the time-frame available, it's worth having a discussion before starting them.  Sometimes a reviewer has pointed out a real flaw and more experiments really are required in order to deal with it.  Other times, a reviewer is just giving "wouldn't it be nice if..." homework.  It sounds like you think it's more the latter, but the editor may disagree.  I would recommend starting with an explanation of why you think your current experiments are sufficient for a significant publication and why the new experiments should be pushed into future work instead.  The discussion with the editor is likely to end up in one of three places:


The editor agrees that the experiments aren't necessary, and you can talk about them as a direction for future work.
The editor decides your paper will be rejected, since you can't do the experiments.
The editor agrees to a "middle ground" where certain critical studies are done (it may surprise you which ones), perhaps with an extension on time to allow you time to do them, and the paper moves forward.


Talking with an editor is taking an additional risk, since your paper might get rejected quickly, but I would recommend a "fail-fast" strategy over putting in lots of time and effort that turns out to be futile because you were working on something that wouldn't be enough to satisfy the editor in any case.