Deep divisions over the European Union's legal order and energy took an EU summit into late Thursday, with eastern member states Poland, Hungary and the Czech Republic standing in defiance against Brussels.
The rule of law issue was especially thorny, with the potential to shake the very foundations of the 27-nation bloc.
The east-west divide was set to continue Friday, when leaders would return to discuss migration, a topic that turned Europeans bitterly against each other when Germany opened its doors to asylum-seekers fleeing war in 2015.
Poland again defended an October 7 ruling by its Constitutional Court that said EU law applied only in specific, limited areas and Polish law prevailed in all others.
The European Commission and countries including the Netherlands, Finland and Belgium countered that the position undermined EU cohesion and was legal cover for Warsaw to strip independence from its judicial branch and roll back democratic norms.
But under the authority of heavyweights France and Germany, a measure of calm prevailed in the row, as they pressed for dialogue with Poland.
Just before the summit started, French President Emmanuel Macron and German Chancellor Angela Merkel held one-on-one talks with Polish Prime Minister Mateusz Morawiecki.
Macron urged Morawiecki "to find a solution in line with our principles and common rules," according to an Elysee official.
Leaders then held a relatively short two-hour discussion on the issue, kicked off by Morawiecki.
"The debate took place in a serene atmosphere," an EU official said on condition of anonymity. The debate "was a step that should help lead to solutions," the official added.
But that was preceded by four hours of wrangling over energy, which was the original main agenda item when the summit was organized.
Europe is struggling to find ways to cope with a global energy crunch while sticking to goals to mitigate climate change.
Diplomats said that Czech Prime Minister Andrej Babis, backed by Hungarian leader Viktor Orban, refused to sign off on the summit conclusions on energy, wanting to get new language on the EU's landmark carbon emissions system, which he opposes.
Orban and Babis are allies of Morawiecki, and Hungary and Poland have a pact to veto any EU moves to punish the other.
The friction from the two disputes soured an EU summit that was likely to be the last for Merkel, who is bowing out to hand over the reins to a new German government being formed following September elections she did not contest.
A group photo of the leaders, socially spaced, nevertheless presented a show of unity that belied the disagreements behind closed doors.
Arriving for the talks, Belgian Prime Minister Alexander De Croo said that "it's very clear that a red line has been crossed" with Poland's stance on the bloc's legal order.
"This discussion really goes to the heart of Europe," he said.
Dutch Prime Minister Mark Rutte and Finnish counterpart Sanna Marin both said it was time to get tough with Warsaw.
They and several other leaders said Brussels should not release 36 billion euros ($42 billion) in pandemic recovery money that Poland badly wants while the issue stood unresolved.
A few said all EU budget money for Warsaw should be subject to an untested conditionality mechanism tying disbursement to member states upholding the rule of law.
One EU diplomat warned that the commission was preparing the mechanism and that "the moment of truth was getting close" for Warsaw.
As he arrived, Morawiecki showed no sign of backing down.
While he said he was "ready for dialogue" he warned: "We won't act under the pressure of blackmail."
Orban gave him his full support, saying the pressure on Poland was a "witch hunt.”
Merkel, who has always urged a cautious approach in her 16 years of EU summits, said she did not want to see the disagreement with Poland end up before the European Court of Justice.
"A cascade of legal disputes before the European Court of Justice is not a solution to the problem of how the rule of law can be applied," she said.