For the European Union to engage in direct talks with Russia, the mandate matters more than the person, foreign ministers said as they gathered in Cyprus for an informal meeting, where the hot-button issue was top of the agenda.

Disunity, they warned, would only play into Moscow's hands and undermine Ukraine.

"I find that it is a trap that Russia wants us to walk into, that we discuss who talks to them, and they are already picking who is suitable and who is not. Let's not walk into that trap," High Representative Kaja Kallas said on Thursday morning.

Kallas implicitly referred to the Kremlin's far-fetched suggestion of former German Chancellor Gerhard Schröder as the bloc's chief negotiator. Schröder is a pariah in mainstream European politics thanks in large part to his continued warm relations with Russian President Vladimir Putin and lobbying for several Russian energy companies.

"Negotiations are always a team effort," Kallas went on. "You have good cops, you have bad cops, you have a strategy on how you go to the table. So that is why the substance is much more important than who."