Russia and Ukraine have failed to conclude a deal on gas prices during talks in Brussels on Tuesday.
They will meet again next Wednesday in the hope of hammering out an agreement in the Belgian capital.
The pricing and number of payments have been sticking points in the past.
Ukraine asked the EU for a loan worth almost 2 billion euros during the meeting.
Russia cut off flows to Kyiv in mid-June over unpaid bills running over 5 billion euros, though flows to Europe were not interrupted.