European Council President Donald Tusk suggested that U.K. lawmakers revoke the country's decision to leave the EU, saying it's the only positive solution left on the table.
His comments came after a historic defeat for U.K. Prime Minister Theresa May, who saw her deal to leave the EU rejected by a margin of 230 parliamentarians.
The approval of the so-called Withdrawal Agreement is seen as essential to ensure that the U.K. doesn't leave the EU in a disorderly fashion, resulting in WTO trading rules. However, the resounding rejection at Westminster increases the possibility that this scenario will actually happen.
"If a deal is impossible, and no one wants no deal, then who will finally have the courage to say what the only positive solution is?" Donald Tusk, the head of the European Council, said on Twitter on Tuesday night, suggesting that the only available outcome to overcome the impasse in the House of Commons is to stop Brexit.
A ruling by the European Court of Justice last month stated that the U.K. can unilaterally stop its decision to leave the European Union.
Prime Minister Theresa May has said on different occasions that it is her deal, no deal or no Brexit. She has until Monday to propose a plan B to the U.K. parliament, after Tuesday's defeat.
Meanwhile in Brussels, officials await for more detail from the U.K. leader.
"I take note with regret of the outcome of the vote in the House of Commons this evening. I urge the U.K. to clarify its intentions as soon as possible. Time is almost up," European Commission President Jean-Claude Juncker said on Twitter Tuesday night.
The European Union has made it clear that it is not willing to reopen the negotiations on the exit agreement. An EU official told CNBC on Tuesday that "at this stage, there is not more we can do."
Leaders from the other 27 EU nations have held meetings to discuss Brexit, mostly since last summer. The most recent summit, in December, ended with clear conclusions that the so-called Irish backstop — the biggest impediment to U.K. lawmakers approving the deal — is only an insurance policy, that it is not meant to be used and if it were, it would only apply temporarily.
The same reassurances were made on Monday in a letter that Juncker and Tusk sent to May. In the three-page letter, both presidents went a step further and confirmed that these commitments on the Irish backstop have legal value.
A spokesman to European Council President told CNBC that the agreement "is and remains the best and only way to ensure an orderly withdrawal of the United Kingdom from the European Union."
— Correction: This article has been updated to reflect that U.K. Prime Minister Theresa May saw her deal to leave the EU rejected by a margin of 230 parliamentarians.