Uzbekistan officially joined the CIS Free Trade Zone, which now includes:
These cover 3.95% of total world GDP (adjusting for Purchasing Power Parity).
News post on the above here: http://en.ria.ru/business/20131228/186017027/Uzbekistan-Joins-CIS-Free-Trade-Zone.html
Kyrgyzstan and Tajikistan are signatories, but are yet to ratify the treaty (0.04% of world GDP (PPP-adjusted).
For comparative: Germany accounts for 3.72% of world GDP (PPP-adjusted), Italy and Spain jointly account for 3.68%.