Cherokee air cond squeeks

Hi

I have a 1999 jeep cherokee sport. It has about 130.000 mi and a straight 6 cyl. 4.0.

My air conditioning unit squeals when I start the car. It takes a few hundred feet for it to stop. Otherwise the unit works fine. Good strong fan and excellent cooling but the squeal is getting worse and more prolonged. If the car is warmed up it won't happen but if I let it sit for a while and re-start it there it is again. I've heard that you can get some coolant that has lubricant mixed in. I would appreciate any suggestions.

Thanks!

J