Europe is scrambling to shore up Ukraine after US President Donald Trump blindsided Kyiv and its backers on the continent by launching efforts with Russia to end the Kremlin's three-year war.

Kallas has proposed that the 27-nation bloc commit to providing Ukraine with a major package of key weaponry -- including air defences, artillery shells and missiles -- as quickly as possible.

EU foreign ministers meeting in Brussels "broadly supported the new initiative for military for Ukraine", Kallas said.

"The details, especially the numbers, will be decided and discussed at the extraordinary European summit on March 6," she said.

Officials said no firm figure had been proposed so far, though the EU's diplomatic arm has raised the current 20 billion euros ($21 billion) given each year by the bloc since the invasion as a "benchmark".

Diplomats said several countries were pushing for the final figure to be considerably higher.

EU leaders are set to meet in Brussels next week for urgent talks on supporting Kyiv and bolstering their own defences after Trump's head-spinning opening to Moscow.

"We have to put Ukraine in a position of strength so that Ukraine is able to say no to a bad deal," Kallas said.

The new arms package risks being blocked by Hungary, which is friendly with both Trump and Russia.

Budapest has already stated opposition to the initiative, saying it would "prolong the war".