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Hungary has blocked €50bn ($55bn; £43bn) in EU aid for Ukraine hours after agreement was reached on starting membership talks.
"Summary of the nightshift: veto for the extra money to Ukraine," Hungarian Prime Minister Viktor Orban posted on social media after talks in Brussels.
EU leaders said talks on aid for Ukraine would resume early next year.
Ukraine is critically dependant on EU and US funding as it continues to fight occupying Russian forces.
The aid blocking was announced by Mr Orban shortly after the EU leaders decided on Thursday to open membership talks with Ukraine and Moldova and to grant candidate status to Georgia.
Hungary has long opposed membership for Ukraine but did not veto that move. A spokesperson for Charles Michel, president of the European Council, said agreement had been unanimous.
Ukraine's President Volodymyr Zelensky hailed the EU decision on membership talks as "a victory" for his country and "Europe".
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