The European Commission announced Thursday it would send a senior fact-finding mission to Moscow and Kiev to shed light on their gas payment dispute, after a previous row disrupted European supplies.
European Commission President Jose Manuel Barroso "has asked a team of senior officials at the commission to travel to Moscow and Kiev," his spokesman told reporters.
The aim of the mission is "to establish all the facts about the situation."
Talks will also be held in the E.U. with gas operators, he said.
A report will then be submitted to E.U. leaders at their next summit in Brussels on June 18-19.
Russian Prime Minister Vladimir Putin warned Wednesday gas supplies to Europe piped through Ukraine could come to a grinding halt soon due to crisis-ridden Kiev's payment arrears.
Moscow has called in recent days on the E.U. to help Ukraine pay for its gas, or face a repeat of the crisis in January when Russia turned off the natural gas taps for two weeks in January, hitting supplies in Europe.
The E.U. relies on Russia for almost a quarter of all the gas it consumes, notably for heating and the power industry, and more than 80% of the supplies transit Ukraine.
Russian gas giant Gazprom had also called on the E.U. to help Ukraine.