Prime Minister Vladimir Putin on Wednesday said that Russia may cut natural gas supplies to Ukraine if Kiev started unauthorized siphoning, news agencies reported.

"If they do not pay for gas consumed in Ukraine, they will not get it. If they don't get it, then gas is likely to be tapped from the pipeline. As soon as tapping is reported, we will cut supplies," Putin said after a meeting with Austrian Chancellor Werner Faymann.

Putin also said that Russia guarantees gas supplies to Europe without interruption only if transit nations could meet their obligations.

"I do hope that our chief transit partner -- Ukraine -- will fulfill all of its obligations in line with the contract signed in January 2009. If the transit countries honor their commitments, no problems will arise on our part," he said.

The prime minister has repeatedly warned of a new gas crisis with Ukraine, saying that Ukraine might not be able to pay for Russian gas.

Russia supplies a quarter of European Union's gas needs, with 80 percent of it pumped through Ukrainian pipelines. Russia cut off gas shipments to Ukraine for nearly two weeks in January over disputes on pricing and transition fees.

Meanwhile, Putin said Russia and Austria are planning to soon finalize an agreement on the South Stream Gas pipeline project. He said that one of the goals of the pipeline project was "to discipline" Ukraine.

"Diversification will make shipments of Russian hydrocarbons more stable and reliable. It will discipline some, including our transit partners," Putin said.

The project aims to transport Russia-produced gas to Europe bypassing Ukraine. The construction of the 14.4-billion-U.S. dollar project is scheduled to start in November 2010 and to become operational by the end of 2015.