The operation of the Vojany-Uzhgorod interconnector between Ukraine and Slovakia in two modes will be ensured thanks to physical switching of compressors and thanks to 'virtual reverse supplies' (backhaul)," Development Director at national joint-stock company Naftogaz Ukrainy Yuriy Vitrenko told reporters in Kyiv on Thursday.

"Earlier it was one flow from Slovakia to Ukraine. Now the interconnector operates in two modes. This means that if there is a flow from Slovakia to Ukraine, the 'virtual reverse mode can be used for this amount [of gas]," he said.

Vitrenko said that the option with the virtual reverse mode implies that there are two companies, one of which seeks to ship a certain amount of gas from the EU to Ukraine and another one – the same amount from Ukraine to the EU. In this case the operators of gas transport systems clear the payments and gas is not moved across the border.

He said that physical switching can be used for the interconnector.

"If there is no incoming flow to Ukraine, they [operators] change the mode of compressors and ensure physical supplies from Ukraine," he said.

The start of the two-mode operation of the interconnector would help increasing the attractiveness of Ukrainian underground gas storage facilities. European companies will be able to freely pump it to Ukraine and then pump it back from Ukraine.