Ukrainian officials said they twice notified the European Secretariat of the Energy Community of its frustration over plans for a natural gas pipeline through Europe that avoids its territory, the Interfax news agency reports.
"Despite the fact that Ukraine has a well-functioning gas transportation system, which provides continuous energy supplies to Europe amid the absence of investment, individual member countries of the Energy Community have got involved in the South Stream project," a letter to Brussels was quoted by the news service as stating.
Russian energy company Gazprom started work on South Stream's construction in December. Gas transit disruptions through Ukraine, brought on by contractual disputes with Gazprom, prompted a move to diversify the European gas transit network.
Europe gets about 20 percent of its natural gas from Russia, though the vast majority of that is transported through Ukraine's gas transit system.
The Ukrainian system delivers about 5 trillion cubic feet of natural gas to Europe each year. South Stream is designed for about 2.2 trillion cubic feet.