Tajikistan's President Emomali Rahmon and Kazakhstan's President Nursultan Nazarbaev have met in Dushanbe a day before a summit of the Collective Security Treaty Organization (CSTO) in Tajikistan's capital.
The two leaders discussed greater economic cooperation and signed a new "strategic partnership" agreement on September 14.
That accord includes regulations on the status of Tajik migrants who work in Kazakhstan as well as measures to increase Kazakh investments in Tajikistan and to enhance cooperation in education.
The presidents of Russia, Armenia, Belarus, and Kyrgyzstan were also due to arrive in Dushanbe.
Russian Defense Minister Sergei Shoigu is also in Dushanbe for the September 15 summit.
The agenda includes the election of the organization's secretary-general and the head of its united headquarters.
Russian President Vladimir Putin planned to meet separately on September 15 with Rahmon and with Kyrgyz President Almazbek Atambaev.