I have been on phone interviews with a major tech company - an offer would be a significant improvement, both in opportunity for self-improvement, to make a difference, as well as in monetary compensation.
Meanwhile, there are prospective projects at my current workplace that would have to be shelved or delayed should I get this offer and, as planned, take it up.
It's basically similar to the situation in this question, with an added twist -- to visit the branch where I will be based I would need a visa, and this section of the requirements in particular involves employment verification:
If you are employed, evidence of your employment. This is usually a statement on company letterhead from your employer stating your job role, length of employment, salary, and the period of approved leave. If your employer is financially supporting your visit, this should also be mentioned on the reference letter. If you are self-employed, you need to provide evidence of your business ownership (such as the business registration or shareholder’s certificate).
I have been in my current job for less than a year, which in my country means I'm not eligible for paid leave yet. I could borrow time off my leave allotment for next year, but between needing to borrow and needing a reference letter, presumably it would be hard to get away without disclosing the purpose of my visit. (note -- I got headhunted for this - unless something is seriously wrong I tend to not hunt for alternative employments until I have been in a job for a year or so).
I'm inclined to just tell my current employer about the prospective offer -- honesty being the best policy, and if the worst happens, the job offer doesn't materialize and I get sidelined at my current job, presumably that's a sign that I shouldn't be staying too long at this job anyway. but I'm really interested in what people would do in this situation.