Kiev and Moscow have been locked in a bitter dispute over gas supplies that has prompted fears of a return to the winters of 2006 and 2009, when Russia temporarily halted gas deliveries to Ukraine and some European countries. Last week Ukraine said it was suspending the purchase of gas from Russia, and relying on supplies from its own storage facilities. But it backtracked on the announcement within days. Russia has said that Naftogaz, Ukraine’s state-owned oil and gas company, owes over $1 billion in unpaid gas bills. Ukraine maintains that Russia charges it more for gas than other European nations.