Theresa May is facing pressure from European leaders to use her party conference speech this weekend to name the month she will trigger article 50, beginning the two-year countdown to the UK’s exit from the EU.

Senior EU figures have been told in private the prime minister wants to trigger the formal start of the talks early in the new year, but so far she has refused to say so in public.

The pressure not to name a date is intense due to the government’s acknowledgement that the UK negotiating position would have to be outlined in the formal letter issued to trigger article 50. As a result, by naming the date she plans to send a letter to Brussels, the prime minister would set herself on an irreversible course before the cabinet has agreed its negotiating objectives.

May is speaking to the Conservative party conference on Sunday, as well as making the closing address on Wednesday, and could use the occasion to signal a timetable. Both Eurosceptics such as Iain Duncan Smith and pro-Europeans such as Nicky Morgan have urged her to provide clarity on the start of negotiations.

The prime minister is also eager that Brexit does not dominate her first conference, or her administration, and yet the issue dwarfs all else in the political landscape.

European leaders ranging from the German chancellor, Angela Merkel, to the Italian prime minister, Matteo Renzi, have drawn a blank in private discussions with her on the shape of her UK exit plans. Most are content with article 50 being triggered in early 2017 since this gives time for the UK to leave before the next round of elections to the European parliament in 2019.

The key trade-off remains whether access to the single market will include free movement for European migrant workers, some form of judicial oversight from EU courts, and contributions – voluntary or otherwise – to Brussels’ budget.

Some European capitals committed to making Britain’s exit as “soft” as possible have been warning that May’s silence on the issue is leaving the ground vacant for hardline Brexiters such as Liam Fox, the international trade secretary, to dominate the British debate.

In private, European leaders suggest compromises on a limited form of an emergency brake to curtail migration from the EU, pointing out that such measures exist inside the Schengen area, but little detail can be discussed until the formal negotiations start.

But May has told European leaders the government does not want to trigger article 50 until she has an agreed cabinet strategy for the talks and an agreed objective. She is also trying to incorporate a “lessons learned” exercise in Whitehall that has looked at why David Cameron failed to win more in his talks with the EU in February. Some advisers believe Cameron should have taken longer and “rushed his fences”.

However, EU leaders say they need a timetable for Brexit soon, partly to assuage the markets but also to allow the EU to work out its own future institutional structures, including tighter cooperation on defence.

Diplomats now sense after a period of confusion that the Department for Exiting the European Union run by David Davis is clearly the dominant voice in Whitehall on Brexit. They have noticed desks are being set up in the department to liaise with specific EU countries, a role that would previously be the preserve of the Foreign Office.

The aim is to track political thinking in the main capitals by staying in touch with key influencers such as Michael Roth, Germany’s minister for European affairs and a member of the SPD, the junior partner in the ruling grand coalition. In a negotiation, intelligence on the thinking of EU countries will be critical, even if the European commission will try to lead the talks.

Some diplomats are disturbed by the Foreign Office being sidelined as they want Boris Johnson’s department to remain a strong voice in multilateral institutions. A weakening of the Foreign Office in the Brexit discussions would weaken the UK voice more widely on the international stage, it is argued.

The pressure to name the date is also coming from the European commission, now that it has set up a detailed team with which to negotiate with the UK.

Michel Barnier, appointed to be the EU commission’s chief negotiator, formally starts on Saturday and has Sabine Weyand, the commission’s deputy director general for trade, to be his deputy. He has also selected Stephanie Riso, an economist in the European commission, to be his principal adviser and Georg Emil Riekeles to be adviser on inter-institutional issues. A Norwegian, Riekeles has worked with Barnier in the past in France when he was minister for foreign affairs. He will be able to advise on the so-called Norway option of being a member of the European economic area (EEA-EFTA).

Significantly, they are all experts in the operation of the EU single market, likely to be the meat and bones of the UK-EU discussion.

The European council, which represents the EU member states, has its own negotiators as has the European parliament, adding further confusion to the complex agreements to be considered.

An argument for delay is that Europe itself is in political flux due to elections on the continent. All three main European political leaders – Renzi, the French president, François Hollande, and Merkel could be deposed, and replaced by leaders with different approaches to Brexit.

But Renzi has called a referendum on constitutional reform for 4 December and at one point said he would resign if he lost, a move that risked turning the referendum into a plebiscite on his leadership and another gathering point for the anti-politics vote. More recently, as his popularity has faded, he has pulled back from that and his coalition partners have said they would not allow him to resign.

In France, the presidential elections look like a fight between rightwing Les Républicains candidates Alain Juppé, a former prime minister, and Nicolas Sarkozy, the mercurial former president. Sarkozy has suggested he would persuade the UK to stay in the EU in a second referendum offering a reformed EU. The candidate of the right is to be chosen in an all-France primary in November, so the UK will have clarity about the intentions of the likely governing party in May.