The Kremlin reacted today to the prospect of Yuliya Tymoshenko becoming Prime Minister of Ukraine by threatening to reduce winter gas supplies.

Gazprom, the state-controlled monopoly, issued a warning that deliveries would be cut unless Ukraine paid a $1.3 billion debt by the end of this month. It accused RosUkrEnergo, the Ukrainian company that receives Russian gas, of breaching the terms of a supply contract.

But the timing of the announcement raised immediate suspicions that Russia was using energy as a political weapon to punish Ukrainians for backing Ms Tymoshenko, its pro-Western adversary in the Orange revolution.

The conflict threatened a re-run of the gas war between Ukraine and Russia in January last year, when Gazprom briefly halted supplies completely. The move sparked panic in the European Union, which gets a quarter of its gas from Russia and recorded an immediate drop in supplies.

A Gazprom spokesman said that it had complied fully with its obligations to Ukraine but RosUkrEnergo had ignored repeated demands to pay its debt. He said: “With the onset of autumn and winter when gas consumption traditionally rises, we are mindful of the need to resolve this issue urgently.

“Given the continued unwillingness of RosUkrEnergo to respect the terms of the contract, Gazprom will be forced to start reducing natural gas deliveries to consumers in Ukraine in case the debt is not settled by the end of October.”

The gas dispute flared as Ms Tymoshenko’s Orange revolution alliance continued to lead her pro-Russian rival Viktor Yanukovych in the elections with more than 97 per cent of votes counted.

Her Bloc Yuliya Tymoshenko (BYuT) and its coalition ally Our Ukraine held 45.1 per cent of the vote, well ahead of Mr Yanukovych’s Party of Regions, with 34.2 per cent.

The Party of Regions was expected to be the largest single party in the parliament, the Rada. But a key coalition ally, the Socialists, fell below the minimum 3 per cent threshold of votes to win seats, leaving Mr Yanukovych with insufficient support to form a government.

BYuT and Our Ukraine, which backs President Viktor Yushchenko, accused their rivals of ballot fraud in eastern and southern Ukraine, the Russian-speaking regions that are the heartland of Mr Yanukovych’s support.

Mykola Tomenko, a Tymoshenko aide, claimed that results were being forged in 11 districts to boost the Socialists’ tally and allow the party to squeeze into parliament to support Mr Yanukovych. The Socialists were at 2.9 per cent, just a few thousand votes short of crossing the threshold.

“The delay is not only a cynical attempt to break the law, but a desire to completely change election results,” Mr Tomenko said.

Ms Tymoshenko’s return to power marks a remarkable political comeback since Mr Yushchenko, her estranged ally in the Orange revolution, fired her as Prime Minister in 2005.

Mr Yanukovych has refused to concede defeat, insisting that he will be Prime Minister again at the head of a broad coalition with smaller parties. A period of intense horse-trading between the parties is likely but the electoral arithmetic looks against him.

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