A Russian air strike on Ukraine on Sunday shook a fragile consensus among the Group of 20 major economies drafting their joint statement at an annual leaders summit in Rio de Janeiro.

European diplomats are now pushing to revisit previously agreed language on the topic of global conflicts after Russia unleashed its largest air strike on Ukraine in almost three months. The United States responded by lifting prior limits on Ukraine’s use of U.S.-made weapons to strike deep into Russia.

The escalating conflict could upset a hard-fought consensus that G20 negotiators reached around 5 a.m. on Sunday, after an overnight push to ready the joint statement for final review by leaders arriving in Rio.

That preliminary consensus after six days of negotiations included streamlined language about global conflicts including the war in Ukraine, focusing on the need to negotiate peace rather than criticism of any participants.

However, sources said even that “simpler” consensus may now be up for reconsideration following the Russian air strike and the prospect of further escalation.

United Nations Secretary-General Antonio Guterres told a G20 news conference in Rio that he continued to support efforts for a “just peace” in Ukraine.

“Our position has been very clear in relation to … avoiding a permanent escalation in the war in Ukraine,” he said.

French President Emmanuel Macron told journalists in Buenos Aires that his focus is backing a Ukrainian response.

“With what is happening today, we must first equip and allow Ukraine to resist. This is the key to the coming days and the upcoming weeks,” Macron said before embarking for Brazil.

“We will stand by Ukraine for as long as it takes,” said Ursula von der Leyen, president of the European Commission, in a Globo TV interview from Rio.

Until Sunday’s air strike, the toughest element of the talks in Rio had been shared language on financing to mitigate global warming, as differences at U.N. climate talks in Azerbaijan spilled over to the G20 summit in Brazil.