Convert the ISO to UDRW format
$ hdiutil convert -format UDRW -o destination_file.img source_file.iso
Prepare the USB stick
$ diskutil list
$ diskutil partitionDisk /dev/disk4 1 "Free Space" "unused" "100%"
Copy the image to the USB stick
$ dd if=destination_file.img.dmg of=/dev/rdisk4 bs=1m
$ diskutil eject /dev/disk4