As Europe recalled what happens when leaders fail to preserve peace on the conflict's centenary, Germany's Angela Merkel urged her peers to compromise with Cameron as he heads for defeat in a row over who will be the European Union's next chief executive.
"I think we can find compromises here and make a step towards Great Britain," Merkel said.
"I repeatedly spoke of a European spirit which is needed and which will help us to find good solutions," she added.
Cameron has been abandoned by key allies in the fight against Juncker including Sweden and the Netherlands, triggering fears his isolation could reinforce a growing push in Britain to exit the EU.
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Keen to avoid public signs of friction at the Ypres ceremony, European Council president Herman Van Rompuy has urged leaders keep the Juncker dispute off the table at commemorations of the 1914-1918 war in the small Belgian town.
Van Rompuy is to step down in November and diplomats and analysts say his replacement by Denmark's young premier Helle Thorning-Schmidt who made headlines with a selfie with Cameron and Barack Obama at Nelson Mandela's funeral might please Britain, though not France.
The remaining appointments may be discussed at yet another summit to be held, probably on July 17.