Which extension should I use - .com or .co.uk ?

Which domain name extension should I use?

I am designing a new web page with news, forum, chat, gallery etc. This is for the British and MAYBE in the future I will expand the website to include USA, Poland, Germany, Holland and some other countries.

I have checked the Domain Name and it is available with .com, .net and .co.uk (this is used in UK) and other endings are also available.
Which extension should I use? Here, I am a bit worried about the search engine indexing.

Thanks

 

Buy both and use .com as your primary domain name because its the most widely accepted TLD.

 

I would register both, but you .com as the main one. Let the .co.uk just redirect to the .com.

 

Perhaps don't let the .co.uk redirect as such, as it could have implications for SE.

What I'd probably do is just have a simple landing page with something like, "Looking for This Forum? We're at ThisForum.com!"