EU leaders on Wednesday warned about the "challenging" Brexit timetable for 2020 as Britain accelerated its progress towards departure.

Speaking at the European Parliament's plenary in Strasbourg, EU Commission president Ursula von der Leyen said that the Brexit transition deadline of December 2020 left "very little time" for the British and European sides to reach a trade agreement.

"In case we cannot conclude an agreement by the end of 2020, we will face again a cliff-edge situation", von der Leyen said. "And this would clearly harm our interests."

It follows a similar warning by the new European Commission president last week.

Following the Conservatives' resounding election victory, the UK is on course to leave the EU by the end of January under the terms of the divorce deal renegotiated by Boris Johnson.

It would have the force of an international treaty and includes safeguards for citizens' rights — those of EU nationals living in the UK, and Britons on the continent.

But the future UK-EU relationship still has to be worked out, and the British government is ruling out an extension of the post-Brexit transition period, due to expire at the end of next year.

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Von der Leyen vowed to "make the most of the short period", announcing: "On February 1, we will be ready to propose a mandate for the negotiations."

Regretting that the UK would become "a third country" in the negotiations, von der Leyen said she hoped the UK and the EU would be "good neighbours" at the end of the process and praised "brave" British MEPs in one of their last EU Parliamentary sessions. "We will miss you", she said.

"At the very end, I hope – for the sake of the European people and the sake of the British people – that we will have an unprecedented partnership", she said.

Warning over citizens' rights

Meanwhile, European Parliament Brexit coordinator Guy Verhofstadt warned that parliament might not automatically vote for the Withdrawal Agreement, and reminded everyone about the issue of citizens' rights, which he said is not "solved".

"Everyone presumes the European Parliament will give automatically its consent to the Withdrawal Agreement", Verhoftstadt said.

"Not if the remaining problems with the citizens' rights are not solved first. Citizens can never become the victims of Brexit."

Verhofstadt added that he has received "hundreds of letters of citizens panicking about their status" and appealed to British PM Boris Johnson to "be generous in [his] victory".

"Grant to all EU citizens the full rights as they have today", Verhofstadt asked Johnson. "Automatically. To all of them. No ‘ifs and buts’."

Verhofstadt said he thought EU member states should grant UK citizens living in Europe similar rights.

Just like the British House of Commons, the European Parliament must vote on the Withdrawal Agreement. A date for its vote has yet to be scheduled.

The British government and PM Boris Johnson will put the agreement to a vote in the British parliament on Friday (December 20).

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