Removing a rusted power steering hose

I'm trying to replace a broken power steering hose on my truck. I was able to remove the nut on the end of the hose that was connected to the power steering pump. However, the nut on the other end of the hose is so rusted that I can't loosen it with a wrench. When I try the wrench just slides over the grooves of the nut because it has rusted so much that it's almost round. I've tried using a vice grip to remove it (as a last resort), but that didn't work either. How do you suggest I remove it?