Greece and Spain are under strong pressure from EU and NATO allies to provide Ukraine with more air defense systems, writes the Financial Times.
The issue will be discussed on Monday at the meeting of EU foreign and defense ministers in Luxembourg.
Earlier, Kiev urgently asked its Western allies to provide seven additional air defense systems, such as the American Patriot or the Soviet S-300, amid intensifying Russian attacks on the country's energy infrastructure.
So far, only Germany has announced the delivery of one Patriot system, which will arrive in Ukraine in the near future, and has called on other countries to donate additional systems.
EU leaders used last week's Brussels summit to personally urge the prime ministers of Spain and Greece to transfer some of their systems to Ukraine, sources told the FT.
"We all know who has them, we all know where they are and we all know who really needs them," one of the publication's sources said.
Poland and Romania, which also have the Patriot, are under less pressure to consider supplying Kiev given their more vulnerable locations, officials said.
Answering questions from journalists about the possibility of Poland joining the initiative to supply Ukraine with Patriot systems, Prime Minister Donald Tusk said it was impossible, but "there are other types of weapons that help protect heaven, and Poland will be active in this".