"I am convinced that to give Ukraine 50 billion euros ($54.70 billion) from the EU budget for five years... That's a bad decision," Orban told a news conference, Reuters reported.
All 27 EU states except Hungary agreed last week to start accession talks with Ukraine despite the war, bypassing Orban's opposition by getting him to leave the room during the summit when the decision was made. Orban confirmed it was German Chancellor Olaf Scholz who suggested this solution.
But leaders could not overcome Orban's resistance to revamping the EU budget to channel 50 billion euros to Kyiv and provide more cash for other tasks such as managing migration.
EU leaders, who would prefer a deal backed by all members but also have a plan B, are expected to revisit the issue at an emergency summit on Feb 1.
"They want to give the money to Ukraine from inside the EU budget, Hungary wants to give it outside the EU budget. They have the possibility - if we don't agree on this - to resolve this outside the budget but don't have the option of resolving this from the EU budget without Hungarian approval," Orban said.
"They have the possibility, 26 members to resolve this with a joint loan outside the budget. If this comes up we will consider what we say."
The EU could continue to help with a workaround that involved a deal between 26 members and Ukraine, which would also deny Budapest access to linked EU funds, such as on migration.
The EU has suspended a large chunk of funds for Hungary over concerns Budapest had damaged democratic checks-and-balances in the country. The EU unlocked some of those funds last week saying Budapest had implemented a reform of its judiciary but about 20 billion euros still remain frozen.
When asked on Thursday, Orban said Hungary would not want to link the issue of suspended EU funds for Budapest over rule of law issues with financing to be given to Ukraine.
"We do not want to link financial assistance to be given to Ukraine with any Hungarian financial issues ... this would also violate the EU principle of loyal cooperation," Orban said.