Google answers your question pretty well in it's post on Working with Multi-Regional Websites.
Specifically on the section of geo-targeting sub-folders (emphasis mine):
Webmaster Tools' manual geotargeting for gTLDs (this can be on a domain, subdomain or subdirectory level);
I would strongly recommend looking at other global sites that do well internationally and look at their approach (sub-domain vs sub-directory) and consider other things like how you would manage language(s) as well.
You would need to pay special attention to the advice given at the bottom of that link:
Websites that provide content for different regions and in different languages sometimes create content that is the same or similar but available on different URLs. This is generally not a problem as long as the content is for different users in different countries. While we strongly recommend that you provide unique content for each different group of users, we understand that this may not always be possible for all pages and variations from the start. There is generally no need to "hide" the duplicates by disallowing crawling in a
robots.txt file or by using a "
noindex" robots meta tag. However, if you're providing the same content to the same users on different URLs (for instance, if both "
example.de/" and "
example.com/de/" show German language content for users in Germany), it would make sense to choose a preferred version and to redirect (or use the "
rel=canonical" link element) appropriately.