Veto came hours after the European Union agreed to open membership talks with Ukraine in a move Hungary opposed.

Leaders meeting in Brussels said they would revisit the issue next month after Orban refused to back the additional funding for Ukraine’s government as it battles to remove Russian forces from its territory.

“Summary of the nightshift: veto for the extra money to Ukraine,” Orban, the closest ally of Russian President Vladimir Putin in the EU, wrote on social media.

The EU’s other leaders agreed to revisit the debate in January.

“We still have some time, Ukraine is not out of money in the next few weeks,” Dutch Prime Minister Mark Rutte told reporters as he left the talks.

“We agreed with the 26 countries. Victor Orban, Hungary, were not yet able to do that. I am fairly confident we can get a deal early next year. We are thinking of late January.”

Rutte said another summit would be convened to reach a deal. Belgian Prime Minister Alexander De Croo stressed that the financial support was vital.

“It is just as important that Ukraine has the means to continue the war and rebuild its country,” he said.

Orban had promised to block the membership talks and the funding for weeks, and the decision was a blow to Ukrainian President Volodymyr Zelenskyy, who failed this week to persuade Republican lawmakers in the United States to approve an additional $61bn for Ukraine.

Most EU leaders wanted this week’s summit to send a clear sign of solidarity with Ukraine amid perceptions, eagerly seized upon and repeated by Moscow, that allies’ support for Kyiv was waning.

Critics have accused the Hungarian leader of holding Kyiv’s survival hostage in a bid to force Brussels to release billions of euros in EU funds frozen amid concerns about Budapest’s commitment to the rule of law.

In what some saw as a last-minute concession, the European Commission, the EU’s executive, agreed on Wednesday to unblock 10 billion euros ($11bn) of the money.

A further 21 billion euros ($23bn) remains out of Orban’s grasp, but he denied that there was any link to Hungary’s intransigence over Ukraine.

“That’s not our style,” he said.

The war in Ukraine has become bogged down on the front lines in the country’s east, where Putin on Thursday claimed his troops were making progress. The country currently has some 617,000 soldiers in Ukraine, he added, after launching its full-scale invasion in February 2022.

Across Brussels, at NATO headquarters, the security alliance’s Secretary-General Jens Stoltenberg warned that the West must continue supporting Ukraine in order to protect the rest of Europe.

“If Putin wins in Ukraine, there is real risk that his aggression will not end there. Our support is not charity – it is an investment in our security,” Stoltenberg said.