Russia agreed to resume gas deliveries to Ukraine through the winter in an EU-brokered deal reached by the three parties in Brussels on Thursday, an EU source said.
The details will be outlined by European Commission head Jose Manuel Barroso as well as the Russian and Ukrainian energy ministers during a press conference announced for 2045 GMT, the source said on condition of anonymity.
Ukraine's debt of $3.1 billion (2.5 billion euros) will be settled in two instalments, one immediately and the other at the end of the year, another source said.
"The Ukrainians have the money to pay," the source added.
The deal sets a price of $385 per 1,000 cubic metres for the duration of the contract, which runs from November this year to the end of March 2015, the source said.
Payments will be made in advance for the following month.
Kiev sought and obtained a guarantee that the price would not change during the contract, the source added.