The Turkish city of Istanbul is hosting a summit bringing together leaders from Turkey, Iran, Afghanistan, Pakistan, Azerbaijan and the Central Asian states of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan.
The 10 countries are grouped in the Economic Cooperation Organization, which seeks to promote regional trade and economic development.
Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari are among the leaders expected to attend.
Iranian President Mahmud Ahmadinejad is attending the summit with his new foreign minister Ali Akbar Salehi, who is also Iran's top nuclear official.
Turkey's foreign minister Ahmet Davutoglu said he had discussed with Salehi the next round of nuclear talks between Tehran and six world powers. The nuclear talks are scheduled to take place in Istanbul next month.
Davutoglu said Turkey was working toward "reducing the environment of tension" over Iran's nuclear program. Iranian officials met in Geneva earlier this month for talks with officials from the United States, China, Russia, France, Britain, Germany and the European Union.
compiled from agency reports