It could be a low or dead battery. The 2000 Sport was notable for causing a heavy draw on the battery when being started and, having one, I found that installing the most powerful battery that will fit is the solution. I got mine from a battery shop specialist. Until I did this the Jeep ate batteries fairly often and of course they failed at the most inopportune time or place. Will your work with a jump start? If so it is a good indication your present battery if low. Good luck.
could be a faulty neutral safety switch in your console, try putting the shifter in neutral, then try starting it, if it works you will need to replace the switch. or could be a problem with fuel delivery...here is a link with a different answer (about halfway down page); http://autorepair.about.com/library/faqs/bl122f.htm
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