Don't do it!
Been there, done that, made a mess. The diesel will burn, but in a very short time, it will heavily soot the inside of the heater. Plus, the flame is lower, (even on a high setting) and you'll get less heat from your heater). Additionally, as it burns, the soot starts to rise from the stove and drift through your house.
Trust me, you're much better finding a reliable source of kerosene - even if it costs more, you'll be better in the long run.