Support for Ukraine is one of European Commission President' Ursula von der Leyen's "red lines" for cooperating with politicians to her right after the June 6-9 European Parliament elections, she said in a televised debate on Thursday.
Von der Leyen had hinted in earlier debates that she might be prepared to work with parliamentary groups to the right of her own centre-right European People's Party.
Support for the EU, for Ukraine, and for the rule of law were von der Leyen's conditions for future cooperation, she said at the final debate among political groups' lead candidates in the European Parliament in Brussels.
Von der Leyen said she'd work with politicians who meet "three criteria: the first is pro-Europe, the second is pro-Ukraine - that is anti-Putin - and the third is indeed pro-rule of law."
That ruled out Marine Le Pen's National Rally in France, the Alternative for Germany (AfD), Revival in Bulgaria, and the Confederation of the Polish Crown (KKP), von der Leyen said.
"All these may have different names and different principles, but they have one thing in common: They are friends of Putin and they want to destroy our Europe. And we will not allow this to happen."
But von der Leyen suggested that she might be prepared to work with Italian Prime Minister Giorgia Meloni, who is standing in the EU elections and whose Brothers of Italy party is affiliated to the European Conservatives and Reformists (ECR) group.
"I have been working very well with Georgia Meloni in the European Council, as I do with all the heads of state and government," she said when asked about Meloni.
"She is clearly pro-European," von der Leyen said. Meloni is also "against Putin - she's been very clear on that one - and pro-rule of law, if that holds. And there we offer to work together."
Another major national affiliate to the ECR is Poland's Law and Justice Party, which governed the country until being ousted by Donald Tusk's centrist coalition in elections last year.
Le Pen's National Rally is affiliated to the Identity and Democracy (ID) group, which is generally further to the right than the ECR. On Thursday, the ID group announced it had expelled the AfD from its ranks, citing the behaviour of AfD lead candidate Maximilian Krah.
Krah had said that not all members of the Nazi-era Schutzstaffel (SS) were criminals. The SS was a Nazi paramilitary organization that was heavily involved in war crimes and ran the regime's death camps during the Second World War, including Auchwitz.
Furthermore, one of Krah's assistants, whom he has since fired, was arrested on suspicion of spying for China's foreign intelligence service.
The other two far-right parties von der Leyen ruled out working with - Revival and the KKP - are not currently represented in the European Parliament.