The Russian and Turkish presidents have witnessed the launch of construction of a new reactor at Turkey's first nuclear power plant.
Vladimir Putin and Recep Tayyip Erdogan watched live over video link as concrete was laid at the third unit of the Akkuyu nuclear power plant in southern Turkey.
Russia's Rosatom state nuclear energy firm is building the plant in Mersin Province on Turkey's Mediterranean coast. The two countries signed a cooperation agreement in 2010 and began construction of the first of four planned reactors in 2018.
The total cost of the project, which has yet to go online, is estimated at $20 billion.
During the ceremony, Putin said he expected the project to "improve the Russian-Turkish partnership in all its facets, helping strengthen friendship and mutual understanding between our countries' peoples."
Referring to Putin as "my dear friend," Erdogan called the power plant project "one of the symbols of Turkish-Russian cooperation."
The Turkish president said the plant's first reactor is scheduled to become operational in 2023 to coincide with the centenary of the Turkish republic.
Erdogan also said construction of the fourth unit will start later this year and added that the project is expected to provide 10 percent of Turkey's electricity when completed.
The two leaders have enjoyed a complex relationship while leading their countries for most of the past 20 years.
Moscow and Ankara have struck a fragile balance in war-ravaged Syria and Libya even as they support opposing sides and are jointly monitoring a cease-fire between Armenia and Azerbaijan in the disputed Nagorno-Karabakh region.