I got a PhD offer from a US university (the same university I completed my undergrad degree), and I asked for a deferral earlier this year (as I'm planning to do a one-year master's program at a UK university) and the professor approved my request. However, in the past few months, I found myself changed my research interest to a relevant field, but it's very different from the US PhD program I deferred.
My question is would that be possible/okay for me to let my university know that I want to decline this offer (which is intended to begin in September 2023) and reapply to other PhD programs that fit better with my research interests? If so, should I do that as soon as possible?
I didn't sign any legal document for the deferral (just sent an email to the program director to confirm I want to take the deferral), but I would feel bad for not committing to their program and applying to others.
Additional information: If I didn't get accepted elsewhere I might still be interested in this position, so I'm not sure when would be a good time to let my professors know I want to decline, and if it's unethical to do that too late.
I might also be asking my professors at the current university for a reference letter if I reapply to other programs (since they know me very well and the new application cycle for PhD is starting soon), so I want to figure out how I can better communicate with my professors about my situation without burning a bridge.