What happens if I cannot meet the STEP requirement for my offer?

Hi all, I am an international student from Singapore, and have recently been granted a conditional offer from Imperial to read Computer Science. The conditions are really strict -- AAAA in all my H2 subjects (we don't have A* so A is the highest grade), a merit in my H3 Pharmaceutical Science, as well as a grade 2 in STEP 1 Math.

I already have met all the other requirements except STEP Math. However, the problem right now is that I have to go for my mandatory national military conscription from next week until around July, so I may not be able to book out of the camp to take the test, especially if it clashes with key military events. Even if I were able to do so, I would also not be able to have ample practice time (apart from certain weekends when I am allowed to book out of camp) to prepare for the test.

What should I do? Should I tell Imperial about my circumstance? Do you think they will still accept me even if I do not meet their STEP requirements?