If you delete it ,you will not loose your indexing,so don't worry. You can re build a fresh one ,then submit,if you use the same method,Google will recognize the links that have been previously indexed.
You can resubmit the sitemap either through google webmaster OR by add the following line in robots.txt. Sitemap: http://www.domainname.com/sitemap.xml Google downloads the sitemap from the location specified in robots.txt automatically. Whenever a new sitemap is either resubmitted or downloaded by google, you will not lose previously indexed pages as long as those URLs are still present in the new sitemap.xml
nci thank you very much , I am very happy for your saying this. lkraj yes,this is reassuring thank you very much .