EU leader Jean-Claude Juncker vowed Wednesday to work until the last moment to prevent a "no deal" Brexit, but admitted Britain crashing out now appears to be a likely result.

Addressing the European Parliament after Prime Minister Theresa May asked for a short postponement, Juncker said London remains on course for Brexit next week.

But he added: "The European Union will not kick any member state out.

"I will personally do everything I can to prevent a disorderly Brexit and I expect political leaders across the EU27 and in the United Kingdom to do the same."

On Tuesday, May asked opposition leader Jeremy Corbyn to help develop a Brexit plan that could be ratified by the House of Commons, and asked Brussels for more time.

Juncker responded that EU leaders would be flexible, but time is limited and a disorderly no-deal Brexit would only be welcomed by populist and nationalist forces.

"In light of Prime Minister May's statement last night, I believe we now have a few more days," he said.

"If the United Kingdom is in a position to approve the withdrawal agreement with a sustainable majority by 12 April, the European Union should be prepared to accept a delay until 22 May.

"Yet I believe that a 'no deal' at midnight on the 12 April is now a very likely scenario. It is not the outcome I want, but it is an outcome for which I have made sure the European Union is ready."