The Organisation for Economic Co-operation and Development (OECD) has invited five nations to start negotiations about membership.
The OECD last accepted a new member in 2000
The 30-nation group has invited Chile, Estonia, Slovenia, Russia and Israel to talks. No time frame has been set.
The OECD has also offered "enhanced engagement programmes" to China, India, Brazil, Indonesia and South Africa with the possibility of future membership.
Enlargement is a way to reflect the shifting make-up of the world economy.
With regard to future expansion, the OECD said priority would be given to South East Asia, because of its "growing importance" in the world economy.
As developing nations' economies have grown, the OECD's share of world trade has fallen - from 75% when it was launched in 1961 to 60% today.
Some 16 nations are looking to join the organisation, which espouses the idea of democracy through the free market.
New members must be agreed upon unanimously. The last new member to join was Slovakia in 2000.