Kazakhstan is expected to sell some of its crude oil through Azerbaijan's biggest oil pipeline from September, as the nation seeks alternatives to a route Russia threatened to shut, Reuters cited three sources familiar with the matter as saying.

Kazakh oil exports account for more than 1% of world supplies, or roughly 1.4 million barrels per day (bpd). For 20 years, they have been shipped through the CPC pipeline to Russia's Black Sea port of Novorossiysk, which provides access to the global market.

In July a Russian court threatened to shut the CPC, prompting the Kazakh government and major foreign producers to set up contracts for other outlets as a precaution. None of the alternatives are as practical as the CPC pipeline, raising the risk of further volatility on energy markets.

Shortly after Russia invaded Ukraine in February, international crude prices hit 14-year-highs and prices have stayed high, sustaining an average above $100 a barrel in July.

A source with direct knowledge of the matter said Kazakhstan's state oil firm Kazmunaigaz (KMG) was in advanced discussions with the trading arm of Azerbaijan's state firm SOCAR to allow 1.5 million tonnes per year of Kazakh crude to be sold through the Azeri pipeline that delivers oil to Turkey's Mediterranean port of Ceyhan.

At just over 30,000 bpd, the volume is a trickle compared to the usual 1.3-1.4 million bpd that flows through the CPC pipeline.

The final contract is due to be signed at the end of August with flows through the Baku-Tbilisi-Ceyhan (BTC) pipeline starting up a month later, the source said.

Another 3.5 million tonnes per year of Kazakh crude could start flowing in 2023 through another Azeri pipeline to Georgia's Black Sea port of Supsa, two sources said.

Combined with BTC flows, the volume would equate to just over 100,000 bpd, or 8% of the CPC flows. KMG declined to comment and SOCAR declined to comment on the specific deal.

Relying on Azerbaijan would allow Kazakhstan to side-step Russian territory. Last month, BP Azerbaijan said it would redirect flows away from the Baku-Supsa pipeline to the larger BTC pipe.

However, the new BTC route means Kazakhstan will have to rely on a fleet of small tankers to take its oil across the Caspian Sea to Baku from its port at Aktau that has limited spare capcity, the sources said.