The European Union heads of state meeting in Brussels Monday remain deadlocked over an oil embargo against Russia, with Hungary the key holdout.  The summit will continues Tuesday.

European Union leaders are reportedly considering a draft proposal that would temporarily exempt crude pipeline deliveries from any oil embargo against Russia, focusing for now on oil shipments. If agreed, the ban would be part of a sixth EU sanctions package against Moscow over the war in Ukraine.

Arriving at the summit, European Commission chief Ursula von der Leyen played down hopes for a quick breakthrough.

“We’ve now basically solved all the issues but one, and this is the question of crude oil by pipeline. And here the discussions are still ongoing. I have not too high expectations that we’re going to solve it in the next 48 hours, but thereafter,” she said.

Underscoring the difficult negotiations, Hungarian Prime Minister Viktor Orban criticized the EU’s executive arm and said there was no agreement so far.

“We are ready to support the package sanctions if there are solutions for the Hungarian supply security we haven’t got up to now,” he said.

Like Hungary, Slovakia and the Czech Republic are highly dependent on Russian energy and also have reservations over an oil embargo. But Hungary’s Orban has been the most vocal.

Until now, the EU has shown remarkable unity as it agrees to ever-tougher sanctions against Moscow.

Estonian Prime Minister Kaja Kallas said more needs to be done.

“As far as the war continues, we haven’t done enough. We have done a lot but still not enough, because still the war continues,” she said.

Some experts wonder just how long the EU’s 27 members will stay on the same page, as the Ukraine war drags on.

“It’s obviously difficult to predict the outcomes of the war just three months after it started, but one can imagine several scenarios of how it evolves, and some of them are highly divisive for Europeans,” said analyst Marie Dumoulin of the European Council on Foreign Relations.

She says EU unity could erode if, for example, there’s a messy and protracted cease-fire between Ukraine and Russia, or if Ukraine wants to retake control or cede areas captured by Russia before or during this war.

Ukrainian leader Volodymyr Zelenskyy is expected to join the summit by video link with European leaders for continuing talks Tuesday.