Emmanuel Macron’s plans for a new European Political Community were almost thrown into disarray by disagreements over where each of the 44 leaders would sit at the summit.
The new forum of EU and non-EU nations, the brainchild of the French president, began in Prague on Thursday.
But officials admitted that finding the right seating plan was a major headache, forcing hours of talks between senior diplomats because of long-standing and new disputes between the countries attending.
"It’s been hard, very hard," said one official, while another said the seating plan was the most difficult thing to organise in the international summit.
Such are the divisions that leaders’ discussions are being split into two separate working groups, which then swap to ensure that certain leaders are not in the same room.
Serbia and Kosovo are both attending the summit, but in a legacy of the break-up of Yugoslavia, Belgrade still refuses to recognise its neighbour as an independent country.
That had to be taken into account when seating the two leaders; Aleksander Vucic, the president of Serbia, and Vjosa Osmani-Sadriu, the president of Kosovo.
No written conclusions
The dispute also had ramifications for other preparations for the summit, which in a sign of abiding divides between leaders, is not planned to end in written conclusions.
No national flags are being displayed at the summit to avoid inflaming sensitivities. And papers listing the names of the leaders handed out to the press did not say which countries they represented in another effort to temporarily patch over the long-running row.
Meanwhile, Turkey is embroiled in a row with Sweden and is threatening to block the country’s application to join Nato.
Ankara accuses Stockholm of harbouring Kurdish terrorists and is threatening to use its veto to stop Sweden ending decades of non-alignment after the invasion of Ukraine and joining the alliance.
The row also has ramifications for Finland, which plans to join Nato at the same time as its near neighbour.
Some other leaders are said to be wary of being seated too close to the authoritarian Mr Erdogan, who is also at very public loggerheads with historic foe Greece.
Kyriakos Mitsotakis, the Greek prime minister, warned on Wednesday that Athens was ready to use troops if necessary to protect its sovereignty, as he hit out at what Greece sees as illegal Turkish drilling in its territorial waters.
The Turkish president, a Muslim, was said to want to avoid being placed near fellow leaders if they are drinking alcohol. He will also refuse to be associated with his Armenian counterpart, over a long-running dispute over genocide.
Matters are further complicated by September’s border clashes between Azerbaijan and Armenia, which are also both at the European Political Community.
On September 12, there were a series of border clashes between Armenian and Azerbaijani troops in a major escalation of a crisis that has resulted in nearly 300 deaths.
The Greeks, Cypriots and Turkish delegations also cannot be placed in the same working groups.
Liz Truss is also attending the inaugural summit of an event meant to foster closer ties between EU and non-EU countries, including Ukraine.
Ms Truss will call on European leaders to stand firm against Russian aggression in what she will describe as the biggest crisis since the Second World War.
She will also hold bilateral talks with Mr Macron on Channel migration in a meeting, which aims to reset relations between Paris and London that have been strained by Brexit.
While the summit in Prague is not expected to yield any major results, officials are said to have already lined up three more meetings, the next being in Moldova, with Spain expected to follow.
Ms Truss had demanded that London be considered as a possible destination in order to convince her to attend the gathering in the Czech capital but it now appears that won’t happen for at least 18 months.