Hungarian Prime Minister Viktor Orban is threatening to block all European Union aid for Ukraine, as well as the country's future accession to the bloc, unless EU leaders agree to review their entire strategy of support for Kyiv, Politico reported with a reference to a letter addressed to President of the European Council Charles Michel.

In the letter, the Hungarian leader says that no decision on funding for Ukraine, the opening of accession talks to the EU, or further sanctions against Russia can be taken until this "strategic discussion" happens when leaders gather in Brussels in mid-December.

"The European Council should take stock of the implementation and effectiveness of our current policies towards Ukraine including various assistance programs," Orban said in the letter, which is undated but bears the stamp of his office.

He also asks why Europe should continue to support Ukraine at a time when the United States, which has provided the bulk of military aid for Kyiv, may not be able to continue funding due to partisan deadlock over future support.

"The European Council must have a frank and open discussion on the feasibility of the EU's strategic objectives in Ukraine. Do we still regard these objectives realistically attainable? Is this strategy sustainable without robust support from the United States? Can we take continuing support from the United States for granted? How do we conceive the security architecture of Europe after the war," Orban said.

He also said that "the European Council is not in a position to make key decisions on the proposed security guarantees or additional financial support for Ukraine, endorse further strengthening of the EU sanctions regime or agree on the future of the enlargement process unless a consensus on our future strategy towards Ukraine is found."

According to Politico, Orban's letter raises the stakes in a long-running standoff between Budapest and Brussels, which is holding back EUR13 billion in EU funds for Hungary over concerns that the country is falling afoul of the EU's standards on rule-of-law.

Without saying so directly, the letter suggests that Budapest could use its veto power to block the disbursement of a planned EUR50 billion in aid for Ukraine – money that's needed to fund the Ukrainian government while its armed forces fight back against a full-scale Russian invasion.

In addition to the EUR50 billion, Orban is threatening to block EUR500 million in planned military aid for Ukraine, as well as the opening of formal negotiations for Kyiv to join the 27-member union, which leaders were hoping to approve at the next gathering of the European Council on December 14 and 15.

According to one EU diplomat who was granted anonymity to discuss confidential deliberations, Orban has "booby-trapped" the entire EU decision-making process on Ukraine as part of a strategy to raise pressure on the European Commission to release the EUR13 billion to Hungary. The diplomat went on to say that while on other occasions, Budapest has abstained on key votes and allowed the EU to slap sanctions on Russia, on this occasion, "I don't see that happening."

"It's not a matter of neutrality for Hungary. It's about leverage," the diplomat said.