I had submitted my site's URL to Google Webmaster Tools. I am using OpenCart. I also have robots.txt file which is accessible to Googlebot.
Now issue I am facing: Googlebot is blocked from accessing 450 URLs by robots.txt but these URLs are present in the sitemap which I submitted. Now I am seeing almost 150 warnings on the "Google Index" page of Google Webmasters Tools.
Will this effect the website indexing? I do not know how to control the sitemap. am using the default sitemap for OpenCart.
robots.txt
is blocking these URL's them presumably you do not want them crawlable/indexable in Google? If that's the case, there isn't a problem. And you do have control over the default sitemap in OpenCart, the platform is open source so you can modify anything you like.