European Union leaders on Thursday reached an agreement to create a 50 billion euro fund for Ukraine, bringing on board Prime Minister Viktor Orban of Hungary, who was the primary obstacle to a deal.

“We have a deal. #Unity All 27 leaders agreed on an additional €50 billion support package for Ukraine within the EU budget,” the president of the European Council, Charles Michel, said on social media just an hour into the meeting. “This locks in steadfast, long-term, predictable funding for #Ukraine. EU is taking leadership & responsibility in support for Ukraine; we know what is at stake.”

What, if anything, Mr. Orban received in exchange for giving up his veto for the fund, valued at about $54 billion, was not immediately clear.

He had been demanding an annual chance to veto the disbursement of money to Ukraine, but that was rejected. Instead, E.U. leaders agreed to a regular review of the way the money was being spent, to assuage concerns about diversion or corruption, E.U. officials said.