Earlier on Friday, Spanish officials in Brussels said Sanchez might not attend the summit if London fails to put into writing a promise that no future agreement between Britain and the European Union that applies to Gibraltar can be signed without first being negotiated on a bilateral basis with Spain.
However, even though European Union leaders approved the deal on Sunday, it needs to be passed by the United Kingdom parliament, where many lawmakers, including from Prime Minister Theresa May's own Conservative Party, vehemently oppose it.
The nearly 800-word message is an attempt to speak directly to the public to build support for her deal, which faces widespread opposition at Westminster including from both wings of her Conservative Party and the Democratic Unionist Party which props up her administration.
"Spain is the physical and geographical gateway to Europe for Gibraltar", Picardo told the BBC.
The Europeans want to secure the same access to fishing waters around Britain that they now enjoy, and have tried to tie the issue to a future trade deal with it.
May used a post-summit news conference to make a sales pitch for her plan, telling television viewers at home that it was the "only possible deal", offering control of United Kingdom borders and budgets while maintaining close cooperation with European Union regulations that was good for business and the security of the broader region. The British leader is under intense pressure from pro-Brexit and pro-EU British lawmakers, with large numbers on both sides of the debate opposing the divorce deal and threatening to vote it down when it comes to Parliament next month.
No better Brexit deal available, EU ministers tell Britain
Readers of an older disposition will know what I mean. 'Any cabinet minister that supports this is not a eurosceptic'. She then suddenly raised stakes, saying that "the choice before us is clear - this deal or leave with no deal".
"There is no plan B. This is the deal on the table and I'm not willing to contemplate defeat in the British Parliament because I have every confidence in Theresa May and the wisdom of the British people".
Rosa Prince, author of Theresa May: The Enigmatic Prime Minister, said May's uncompromising style has not always gone down well in Westminster but the public has come to admire it.
Liberal Democrat Brexit spokesman, Tom Brake, said: "The prime minister has caved in once again".
She used her keynote speech at the DUP's annual conference in Belfast to reject the government's proposed deal and said it must be improved in the weeks ahead.
Spain threatened at the last minute to withdraw from the summit until it was given assurances over trade arrangements with Gibraltar - a British overseas territory with 30,000 residents.
British Prime Minister Theresa May, who has faced relentless criticism over her handling of Brexit and seen multiple Cabinet members leave as a result of negotiations, echoed Juncker's calls to accept the deal.
With the 585-page withdrawal agreement dealt with among negotiators and a vague statement on future relations both ready to be rubber-stamped on Sunday, Spain belated demands on Gibraltar had been taking center stage.
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Abrams has been embroiled in a legal battle with Kemp and the state of Georgia ever since the midterm elections on November 6. Ironically, this time around, it seems Democrats are having a tough time coming to terms with election results.
The U.K. Telegraph reported that the British government has conceded in writing that no part of any future trading agreement can apply to Gibraltar without the agreement of the Spanish government - leading to fears that the Spanish may use that power to extract a deep range of concessions on issues such as taxation and fishing.
"Parliament will have the chance to do that in a few weeks´ time when it has a meaningful vote on the deal", the prime minister said.
Britain could also simply crash out on March 29.
Britain remains deeply divided over the decision, but the prime minister said that finally leaving could be "a moment of renewal and reconciliation".
May hopes to leave Brussels on Sunday with the terms of British withdrawal on March 29 and a comprehensive concept for future Britain-EU relations settled with the bloc.
"This puts Spain in a position of strength in negotiations with the United Kingdom over Gibraltar that we have not had until now", Mr Sanchez told reporters after the summit.
"Even the people that people who voted for Brexit they are not happy with this deal".
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At the People's Choice Awards on Sunday, stars called for prayers and donations to help residents and rescuers. The Camp Fire in northern California has killed at least 71 people. "I mean they're suing him", he said.
Donald Tusk, the president of the European Council, tweeted on Saturday afternoon that there was unity and solidarity from the EU side.