How to avoid winrm error, in my decommission script

How can I delete sites and their apppools remotely from an IIS server?

Invoke-Command -ComputerName $server {Remove-Item -recurse "IIS:\Sites\$site"} 

Error Received:

WinRM cannot process the request. The following error with errorcode 0x80090322 occurred while using Kerberos authentication: An unknown security error occurred.