Nato is undergoing one of the greatest changes since it was formed in 1949.

Seven eastern European countries - Estonia, Latvia, Lithuania, Bulgaria, Romania, Slovakia and Slovenia - have been formally invited to join the alliance in 2004.

Another three countries - Croatia, Albania and Macedonia - hope to join the organisation in the next few years.

Click on a country name on the map
to find out more

See also:
Q&A: Nato expansion
Quick guide: Nato