Russia said Friday that gas drilling technology likely to be used by Ukraine could pollute water supplies for Russians living near the border between the two countries.
Ukraine is expected to employ hydraulic fracturing, a widely used but controversial process that involves blasting a chemical solution into rock formations to release gas, Russia's Natural Resources and Environment Ministry said in a statement.
Hydraulic fracturing, or fracking, near Ukraine's border with Russia could pollute surface and underground water reserves used by local people, the ministry said.
Ukraine depends on Russian imports of natural gas, but in recent years has been attempting to diversify its supplies by financing alternative sources of the fuel, particularly domestic reserves of shale gas.
The exploitation of shale gas, which is locked in shale rock formations, has revolutionized the world gas market in recent years and threatened the traditional dominance of fixed pipeline suppliers like Russia.
Ukraine signed two major shale gas deals with international oil giants Shell and Chevron last year worth a combined $20 billion.
Russia slashed the price Ukraine pays for gas by about a third last month in a deal concluded by President Vladimir Putin and his Ukrainian counterpart. The agreement marked a renewal of economic ties between Kiev and Moscow that some analysts suggested could jeopardize Ukraine's appetite for shale gas development.
Russia's abundant natural gas reserves mean that it does not need to use fracking in the gas industry, but the process has for decades been employed widely by Russian oil companies to maximize crude production.
A boom in natural gas output in the United States in recent years has been underwritten by the use of fracking, which has come under fire from environmentalists for its allegedly harmful ecological consequences.
Fracking plans have caused public outcries in several European countries, and the technology was banned by France in 2011.