President Vladimir Putin has warned that Russia will cut gas supplies to Ukraine if it fails to pay in advance for future deliveries.
Putin said Wednesday that Ukraine's latest payment would only be good for another three to four days, warning that the cutoff may disrupt transit to Europe.
Following a bruising price and debt dispute, Russia and Ukraine signed a deal in October requiring Kiev to pay in advance for gas shipments.
Last week, Russia accused Ukraine of cutting gas supplies to rebel-controlled areas in the east. Russia then started direct supplies to the east, saying they should be counted as part of the overall volume of its gas exports. Ukraine has rejected the argument, saying that it can't control gas distribution in areas outside its control.