Hungary's Prime Minister Viktor Orban. (Photo: AP)

At a summit in Brussels, other leaders bypassed objections from Hungarian Prime Minister Viktor Orban by getting him to leave the room while they took the historic step of agreeing to start accession negotiations with a country in conflict. But they could not overcome resistance from Orban to a revamp of the bloc's budget to channel vital financial support to Ukraine and provide more cash for other EU priorities such as managing migration.

They ended talks on the financial package, which requires unanimity of the 27 EU leaders, in the early hours of Friday morning and said they would try again in January, with some voicing optimism a deal could be clinched then.

Orban has argued Ukraine should not get such large amounts of money from the EU budget as it is not part of the bloc.

Other leaders have assured Kyiv they channel aid to Ukraine outside the EU budget if Budapest maintains its blockade.