Russian President Vladimir Putin has arrived in Tajikistan's capital, Dushanbe, where he will attend a summit of the Commonwealth of Independent States (CIS) on September 28.
Putin's aide Yuri Ushakov told reporters earlier that the summit will open on September 27 with an informal dinner at a government residence.
The leaders are expected to discuss difficult issues, "including rather sensitive ones," Ushakov said.
Putin came to Dushanbe from Azerbaijan's capital, Baku, where he was on a brief working visit.
The presidents of Azerbaijan, Belarus, Kyrgyzstan, Kazakhstan, Moldova, Uzbekistan, and the prime minister of Armenia have confirmed their attendance.
Turkmenistan will be represented by a deputy prime minister.
The CIS, a regional intergovernmental organization, was formed following the collapse of the Soviet Union in 1991.
Ushakov also said that Putin would meet on the sidelines of the summit with the presidents of Tajikistan and Kyrgyzstan -- Emomali Rahmon and Sooronbay Jeenbekov, respectively.
A meeting with Moldovan President Igor Dodon is also planned for September 27, Ushakov said.
Some 18 documents are expected to be adopted during the summit.
Preparations for 2020 celebrations to mark 75 years since the end of World War II will receive special attention, Ushakov said.