How many Countrycodes could be entered?
First of all, i would remove all special chars like '-', to get a clean input.
Then i would do a check to the length. If the length is over 10 digits, then its a countrycode included. Then you check again the Regex with Countrycode. And if not, use the second regex.
Pseudocode:
if input.length > 10
Regex = ^\d{1,2}\d{10}$
else if input.length = 10
Regex = ^\d{10}$
else
crap input