BAKU, Azerbaijan—Azerbaijan launched the first phase of a pipeline project on May 29 to supply gas to Turkey and southern Europe, part of a European effort to reduce reliance on Russian energy supplies.

The Southern Gas Corridor pipeline project, which involved a $40 billion investment, will supply about 6 billion cubic meters (Bcm) of gas a year to Turkey and, by first-quarter 2020, another 10 Bcm a year to Europe.

The gas is being lifted from Azerbaijan’s Shah Deniz field.

The pipeline will compete with the Russian-built TurkStream pipeline that is due to become operational at year-end 2019.

Russia’s Gazprom now supplies about 34% of Europe’s gas market, the company’s main source of revenue.

TurkStream’s first line, with a capacity for 15.75 Bcm a year, will supply Turkish consumers. In a second phase, it will supply the same amount of gas across Turkey to southern Europe.

The rival project, the Southern Gas Corridor, could be extended if promising new Azerbaijan gasfields, such as Absheron, could be developed, officials have said.