Google Sitemap Pending?
Not to panic if your sitemap isn’t being approved. It’s a known issue that Google is working on.
Webmaster Help Forum Announcements: Known issue: Submitted Sitemap files stay “pending”

Not to panic if your sitemap isn’t being approved. It’s a known issue that Google is working on.
Webmaster Help Forum Announcements: Known issue: Submitted Sitemap files stay “pending”

Thanks for your info. After waiting more than 24 hours, Google response successfully index atom.xml sitemap.