Gazprom said on Monday it has postponed until Tuesday evening its deadline for Ukraine to pay its $1.5 billion natural gas debt, after which the Russian company has threatened to reduce supplies, according to RIA Novosti.

      Gazprom spokesman Sergei Kupriyanov said the cutoff would apply only to the Russian gas supplied on the border with Ukraine, which makes up 25% of the total. The other three quarters is pumped from Central Asia.

      The spokesman told Ekho Moskvy radio that talks on the debt will be resumed on Tuesday, and that the deadline has been moved from 10:00 a.m. Moscow time (7:00 a.m. GMT) to 6:00 p.m. (3:00 p.m. GMT).

      The head of Ukraine`s state-owned oil and gas company Naftogaz, Oleh Dubyna, started talks in Moscow earlier on Monday with Gazprom CEO Alexei Miller, in a last-ditch attempt to resolve the debt row. Ukrainian President Viktor Yushchenko is set to arrive in the Russian capital later in the day.

      Kupriyanov said: "Progress in the talks has shown that it is hard to expect all problems to be resolved today."

      Gazprom and Ukraine agreed in December that a mixture of Russian and cheaper Turkmen gas sold via RosUkrEnergo would cost $179.5 in 2008. The trader said later it would sell Russian gas to Ukraine in January-March for $314 to cover a shortfall in Central Asian supplies.

      However, the spokesman said the company could agree on new schemes for deliveries to Ukraine if they are not detrimental to the company.

      "As to new proposals, our position is that the situation must not worsen for Gazprom. We are ready to discuss proposals that would not be worse for Gazprom in economic terms, and would ensure secure supplies," Kupriyanov said.

      Naftogaz denied on Friday it had any debts to Russia, and the country`s Prime Minister Yulia Tymoshenko blamed RosUkrEnergo - the sole supplier of gas to Ukraine which is co-owned by Gazprom and Ukrainian businessmen - for the debt.

      She also said she would press for an independent audit of intermediary companies involved in Ukrainian-Russian natural gas deals.