The EU’s plan to offer the UK an extension until 31 January on Friday is expected to be put on hold after Boris Johnson threatened to pull the Brexit deal if Jeremy Corbyn rejects a general election.

Sources said the dramatic developments in Westminster needed to be fully understood and the choreography in Brussels could change.

Donald Tusk, the European council chairman, had been expected to announce on Friday morning, following a meeting with ambassadors, that the EU27 had accepted the delay requested in a letter reluctantly sent by Johnson last Saturday. But senior EU sources said the developments in London had left the situation in flux. An announcement is expected on Monday or Tuesday.

Suggestions that the Labour leader could reject Johnson’s demand for a general election on 12 December provoking the prime minister to pull his deal set alarm bells ringing.

Sources said the French government wanted to see the outcome of the vote on a general election before making a decision, but that the other 26 member states were ready to grant the three-month extension.

The final offer could differ from the extension requested in the Benn act by specifying that the UK could leave on 15 November if the deal was ratified in the UK and European parliament.

Before Johnson’s ultimatum to the Labour leader, the EU looked set to offer a three-month extension, which could be cut short at the point at which the Brexit deal was ratified.

It remains the most likely outcome. “We don’t want to be dragged into British politics and this is what was requested,” said one senior EU diplomat. “They can leave earlier if they ratify the deal. To echo your prime minister, we just want Brexit done.”

But France’s EU minister, Amélie de Montchalin, told RTL radio that clarity over the next steps in London were needed for decisions to be made in “the next hours and days”.

She said: “Our position is that simply giving more time – without political change, without ratification, without an election – would be useless … The French position is to give more time if it is justified, if we understand why more time is needed. That could be more time to ratify, because there’s a deal on the table. Or it could be because they say want to hold elections. Then we’ll look at that.

“But it’s one thing to say we’d like to maybe have elections and another thing to say elections have been organised … Simply giving more time alone leads to getting stuck in a rut. If there’s a clear scenario that will change things, for example a ratification or elections – not just suggested but organised – then we can take decisions.

“But we ask Britain for facts - we’re not in fictional politics, we need facts to make decisions. Decisions will be taken in the next hours and days in terms of what the UK parliament says and what has really been actioned [in the UK]”.