EU may refuse informal Brexit talks until UK triggers article 50

London and Brussels appear headed for stalemate going into a European Unionsummit on Tuesday discuss Britain’s vote to leave.

With Europe’s leaders divided over how to negotiate Brexit and Britain apparently reluctant to initiate formal talks on leaving, an EU source said lawyers had concluded that a member state could not be forced to launch the process.

But a senior EU official stressed that, by the same token, Brussels could refuse overtures for even informal talks before the exit process is officially initiated – a course that prominent Brexit leaders including Boris Johnson want to pursue.

“As long there is no notification, there will not be any negotiations,” the official said. Brussels has given up hope that Britain could be bounced into triggering article 50 – the untested procedure that governs how a member state leaves the bloc – at the summit starting on Tuesday.

The official said the UK was in “a significant crisis” and it would be unrealistic to expect such a move. But he insisted: “We are ready to enter into this process quickly. We are ready to enter into this process as soon as possible.”

The US Secretary of State, John Kerry, is due in London for talks later on Monday after a stop-off in Brussels, while the leaders of Germany, France and Italy will meet in Berlin ahead of the Tuesday summit. Kerry urged both Britain and the EU to “minimise disruption” by negotiating the divorce responsibly.

David Cameron is due to explain the UK’s position at a dinner at the EU summit on Tuesday night. Cameron will leave after the dinner, taking no part in the talks between leaders of the bloc’s 27 remaining members on Wednesday.

Martin Schulz, the president of the EU parliament, led the call for formal exit talks to be launched as early as Tuesday. “We expect the British government to deliver now,” he told Germany’s Bild am Sonntag. “The summit on Tuesday is the appropriate moment to do so.”

The European commission president, Jean-Claude Juncker, said talks should start as a matter of urgency. An EU source told the Guardian that Juncker had called Cameron on Friday to say the prime minister should trigger article 50 immediately.

Cameron said in his resignation speech that he would leave that task to his successor, expected to be named by October. According to the source, Juncker told him: “The decision of the British people was crystal clear, and the only logical step would be to implement their will as soon as possible.”

But EU officials said any chance of exit talks beginning imminently was slight. Lawyers had concluded that a member state could not be forced to take the “grave and irreversible” step of starting the article 50 process, one EU source said, adding that notification “has to be done in an unequivocal manner, with the explicit intent to trigger article 50”.

London is now certain to face severe political pressure to begin negotiations by the autumn and the EU may well reject the idea of informal talks before official notification is made.

Prominent leave supporters including Johnson have said they want to open informal negotiations first in order to avoid locking Britain into the strict two-year timeframe within which article 50 negotiations must be concluded.

In a flurry of further diplomatic activity, Donald Tusk, the European council president who will chair this week’s summit, is due to meet France’s president, François Hollande, on Monday morning, then travel to Berlin to meet Angela Merkel, the German chancellor, and Matteo Renzi, the Italian prime minister, in the afternoon.

With frustrations mounting at Britain’s unwillingness to begin the divorce proceedings, Merkel has called for calm, businesslike discussions, making clear the timing should be up to London.

It is not clear whether Cameron’s successor will seek to keep Britain in the EU single market and so remain subject to EU freedom of movement rules, or press ahead with a total break, the policy of the official leave campaign. Merkel wants to wait until this is known, which may not be until a new prime minister is named.

Merkel is concerned that other EU leaders may try to use the rebuff for Europethat Brexit symbolises as a lever to demand looser fiscal deficit rules on public investment, something both the French and Italian leaders believe could revive the European economy and the popularity of the EU.

Merkel’s chief of staff, Peter Altmaier, said politicians in Britain should “take the time to reconsider the consequences of the Brexit decision – but by that I emphatically do not mean Brexit itself”. Europe should “wait for this to happen with calm”, he said.

Finland’s former prime minister Alexander Stubb said the EU should not push Britain too fast into launching a formal exit procedure. “This will be an extremely complicated set of negotiations,” he said.

Other European capitals, however, are pushing for a rapid exit. The foreign ministers of the EU’s six founding members want Britain to start proceedings “as soon as possible” to avoid a long and potentially damaging period of uncertainty for the already weakened bloc.

The Dutch foreign minister, Bert Koenders, told the Volkskrant on Sunday: “We can’t have the kind of dithering Boris Johnson is suggesting. Everyone wants clarity: people, businesses, financial markets.” France’s foreign minister, Jean-Marc Ayrault, said Cameron should be replaced in “a few days”.

The French and the Italians, facing imminent electoral tests, want to be seen to be responding to popular anger towards the EU and at the same time to take a tough line with the UK in order to underline the cost of leaving the EU. Renzi has called a referendum on constitutional reform in October that might lead to his resignation, while France has presidential elections next spring.

The German vice-chancellor, Sigmar Gabriel, told the Handelsblatt business newspaper that the EU would not be making any fresh offers. “The British have now decided to go. We will not hold talks about what the EU can still offer the Britons to keep them in,” he said, describing Cameron’s decision to call the referendum “a grand and historic blunder” and saying he should step down soon.

“It is clear: you can’t be a bit pregnant. Nor have half a partnership,” he was quoted as saying.

Senior diplomats – so-called sherpas – of the EU member states were meeting in Brussels on Sunday for the first time without Britain to prepare the two-day summit, which aims to send the message that the EU is united following the UK’s unprecedented decision.

Officials have stressed that the UK will not be able to conclude a trade deal with the EU until it has left the union.

France and Germany have reportedly drawn up a 10-page document outlining three key areas – security; migration and refugees; and jobs and growth – for members to address at the summit in an attempt to shore up the 60-year-old union, which faces the risk of unravelling following Britain’s vote to leave.

On Saturday, Tusk appointed a Belgian diplomat, Didier Seeuws, to start work on coordinating future negotiations with Britain.