The European Union will delay Brexit until February 2020 if Boris Johnson is unable to get his deal past MPs this week.

Diplomatic sources said that the delay would be “fungible” meaning that Britain could leave earlier, on the 1st or 15th of November, December or January, if his deal is ratified before the extension ends.

No decision will be taken until EU governments have the chance to assess the chances of the withdrawal treaty getting through parliament before Tuesday this week. If the prime minister runs into serious trouble or MPs force a second referendum then countries led by Germany will push for a longer extension, possibly until June next year.

Norbert Röttgen, chairman of the German parliament’s foreign affairs committee and a senior figure in Angela Merkel’s Christian Democrats, will back a long delay. “The European Council should now grant a final long one, giving the UK time to sort itself out to prepare for all possible resolutions including a second referendum,” he said.

Antti Rinne, Finland’s prime minister and holder of the EU’s rotating presidency will be working with Donald Tusk, president of the European Council to consult capitals over the next “few days.” He said it made sense to allow extra time.

Peter Altmaier, Germany’s economy minister, who is close to the German chancellor, warned that the political “power poker” game in Westminster endangered jobs and prosperity.

“If an extension by a few weeks is necessary, I wouldn’t have a problem with it,” he said.

The EU’s most likely option, according to diplomatic sources, is to decide that the three-month extension in the Benn act, until January 31 2020, is a purely “technical extension”.

Such a decision might not, after internal European talks later this week, even require EU leaders to hold an extra summit on Monday, October 28, and could be agreed via the exchange of letters by ambassadors to Brussels.

The EU will have to hold an emergency summit if a longer political extension is needed beyond February because Johnson’s deal has become bogged down in the Commons or MPs reject it without either legislating for a new referendum or to revoke Article 50.

The main political question for the EU, especially for France. would be the “purpose” of another long extension. Amelie de Montchalin, the French European affairs minister, told the Journal du Dimanche newspaper that the “political uncertainty” had to end.

“We should stop believing that it’s in everybody’s interest to put everything on hold for six months and everything will be better after that,” she said.

European ambassadors met this morning to discuss Brexit in a meeting that lasted just 15 minutes and that took place without any discussion of a possible future delay.

Tusk told European movements that consultations will last until later in the week as the EU assesses progress in Commons votes before taking any decision.

Ambassadors referred a translated and legally checked text of the new withdrawal treaty to the European Parliament for ratification this week, mirroring the government’s push to get the deal across the line.

The parliament’s Brexit committee, chaired by Guy Verhofstadt, will meet tomorrow afternoon to decide if MEPs will go ahead with ratification as soon as Thursday.