SEO Advice.. Going global and the duplicate content issue

Hey everyone,

I have been doing online marketing and seo for years now and I'm always learning something new which is fantastic.

A client of mine has a .com site which is Australian based and is ranking well in google.com.au and aussie searches.

Now they want to take it global and create sites for .co.uk, .com.au, and .com.

They have asked me for the best approach in doing this.

I originally suggested to create separate sites each one with different content so there are no duplication issues and to host each site in servers that are located in the associating country.

Second is the issue of the .com domain name now needing to target US traffic. I cant exactly do a 301 redirect to the .com.au site because the .com site is still going to be used!

But what do you guys think? Is there are better way? What if you break the site up into clientsite.com/au, clientsite/uk etc? Would this be less effective on an SEO level? I'm assuming it will but what are your thoughts?

Any suggestions or ideas you can throw my way would be awesome.

Cheers