European Commission President Jean-Claude Juncker | John Thys/AFP via Getty Images Jean-Claude Juncker: EU won’t renegotiate Brexit deal The Commission president repeated that the Brexit deal was ‘the only deal possible.’

No. More. Negotiation.

European Commission President Jean-Claude Juncker pointedly warned the U.K. that there would be no renegotiation of the Brexit Withdrawal Agreement despite Prime Minister Theresa May's failure so far to win enough support to ratify the deal in the British parliament.

Speaking in the European Parliament in Strasbourg, Juncker expressed unhappy surprise that Brexit would once again be a subject of conversation at an EU leaders' summit this week — this time as a result of May's decision to delay a ratification vote that had been scheduled for Tuesday evening.

Juncker also forcefully defended the so-called "backstop" provision on the Ireland-Northern Ireland border which has been the focus of opposition among British MPs.

The Commission president's blunt remarks, echoing comments on Monday by European Council President Donald Tusk raised questions about how any so-called "assurances" that May might receive this week in Brussels will change the dynamic in London. It essentially means more than 100 MPs would have to shift their position based on the thinnest veneer of political stagecraft, or May will still not have the votes.

"There is a surprise guest at the European Council, which is Brexit," Juncker said in the plenary of the European Parliament in Strasbourg. "I am surprised because we had reached an agreement on the 25th of November, together with the government of the United Kingdom."

"The deal we have achieved is the best deal possible — it's the only deal possible," Juncker declared, pausing as applause echoed through the plenary. "So there is no room whatsoever for renegotiation."

"But there is room," Juncker added, "if used intelligently, there is room enough to give further clarification, and further interpretations without opening the Withdrawal Agreement. That will not happen. Everyone has to know that the Withdrawal Agreement will not be reopened."

On the backstop, which is intended to prevent the recreation of hard border on the island of Ireland and protect the Good Friday Peace agreement in the absence of a larger deal between the U.K. and EU on their future economic relationship, Juncker said: "We have a common determination to do everything to be not in a situation to one day use that backstop."

But he was adamant it could not be discarded from the deal. "We have to prepare. It’s necessary. It’s necessary for the entire coherence of what we have agreed with Britain, and it is necessary for Ireland. Ireland will never be left alone. “

He was followed by the leader of the European People's Party group, Manfred Weber, who is also the conservative candidate for Commission president in next year's European election. Weber accused the British government of trying to reopen negotiations and said enough time had been expended on Brexit already.

"Now, now we see again, a try of renegotiating the whole thing," Weber said. "I think we lost already too much time discussing Brexit."

He added, "We don't play this game."

Weber dryly noted that if the U.K. side was demanding further reassurance and clarification, the EU should similarly demand clarification from Britain about what it actually wants in terms of a future economic relationship — which remeains a subject of continuing disagreement.

"If we can have clarity on these points, it would help a lot to speed up these negotiations," he said. "When the British colleagues are asking for additional clarifications we can also consider to do so."

European Parliament President Antonio Tajani, responding to Juncker, said that his institution was in agreement. “The Parliament is exactly in line with you when it comes to Brexit,” Tajani said.

“The unity of the European Union and its institutions, its 27 member states, is something that is important to all of us. And I am sure the Council will repeat this position. It’s good to have discussions to meet with Mrs May but we won’t be changing a position which has now been adopted. “