Russia could cut off gas supplies to Ukraine by the end of the week, if it does not get further payments from the country. Following a bruising dispute over prices and debt that raised fears of supply disruptions in Europe, Russia and Ukraine signed a deal in October requiring Kiev to pay in advance for gas shipments. It's unclear whether Ukraine, which is on the brink of bankruptcy, is capable of paying. Last week, Russia accused Ukraine of cutting gas supplies to areas in the east controlled by Russia-backed rebels. In response, Russia started pumping gas directly to the east this week, saying the supplies should be considered a part of the overall volume of its gas exports. Ukraine protests that it can't manage gas distribution in areas outside its control.