Here in Riga we will make it clear to them that NATO's door remains open and I believe that at our next summit in 2008 we will extend invitations to those countries that will be ready for membership. Today Croatia, Albania and Macedonia are participating in the Membership Action Plan and the United States supports their aspirations to join the alliance, Bush said in the Latvian capital.
The US president was speaking at a conference entitled "Transforming NATO in a New Global Era" ahead of a summit of 26 NATO member states due to start on Tuesday evening.
He also supported Georgia and Ukraine in their efforts to join NATO, and called for stronger cooperation with Russia.